[Feature] Provide SSLSocketFactory in HttpClient (#333)

## Changes
<!-- Summary of your changes that are easy to understand -->
We need to provide a way for clients to specify their own SSL socket
factory in case they want to handle TLS connections in a different way

## Tests
<!-- How is this tested? -->
Unit tests and local testing

databricks-sdk-java/src/main/java/com/databricks/sdk/core/DatabricksConfig.java

@@ -184,7 +184,7 @@ private void initHttp() {
       return;
     }
     // eventually it'll get decoupled from config.
-    httpClient = new CommonsHttpClient(this);
+    httpClient = new CommonsHttpClient.Builder().withDatabricksConfig(this).build();
   }
 
   public synchronized Map<String, String> authenticate() throws DatabricksException {

databricks-sdk-java/src/main/java/com/databricks/sdk/core/commons/CommonsHttpClient.java

@@ -25,6 +25,7 @@
 import org.apache.http.*;
 import org.apache.http.client.config.RequestConfig;
 import org.apache.http.client.methods.*;
+import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
 import org.apache.http.entity.InputStreamEntity;
 import org.apache.http.entity.StringEntity;
 import org.apache.http.impl.client.CloseableHttpClient;
@@ -36,18 +37,101 @@
 import org.slf4j.LoggerFactory;
 
 public class CommonsHttpClient implements HttpClient {
+  /**
+   * Builder for CommonsHttpClient. This class is used to construct instances of CommonsHttpClient
+   * with configurable parameters for the underlying Apache HttpClient.
+   */
+  public static class Builder {
+    private DatabricksConfig databricksConfig;
+    private Integer timeoutSeconds;
+    private ProxyConfig proxyConfig;
+    private SSLConnectionSocketFactory sslSocketFactory;
+
+    /**
+     * @param databricksConfig The DatabricksConfig to use for the HttpClient. If the
+     *     DatabricksConfig has an httpTimeoutSeconds set, it will be used as the default timeout
+     *     for the HttpClient.
+     * @return This builder.
+     */
+    public Builder withDatabricksConfig(DatabricksConfig databricksConfig) {
+      this.databricksConfig = databricksConfig;
+      return this;
+    }
+
+    /**
+     * @param timeoutSeconds The timeout in seconds to use for the HttpClient. This will override
+     *     any timeout set in the DatabricksConfig.
+     * @return This builder.
+     */
+    public Builder withTimeoutSeconds(int timeoutSeconds) {
+      this.timeoutSeconds = timeoutSeconds;
+      return this;
+    }
+
+    /**
+     * @param proxyConfig the proxy configuration to use for the HttpClient.
+     * @return This builder.
+     */
+    public Builder withProxyConfig(ProxyConfig proxyConfig) {
+      this.proxyConfig = proxyConfig;
+      return this;
+    }
+
+    /**
+     * @param sslSocketFactory the SSLConnectionSocketFactory to use for the HttpClient.
+     * @return This builder.
+     */
+    public Builder withSslSocketFactory(SSLConnectionSocketFactory sslSocketFactory) {
+      this.sslSocketFactory = sslSocketFactory;
+      return this;
+    }
+
+    /** Builds a new instance of CommonsHttpClient with the configured parameters. */
+    public CommonsHttpClient build() {
+      return new CommonsHttpClient(this);
+    }
+  }
+
   private static final Logger LOG = LoggerFactory.getLogger(CommonsHttpClient.class);
   private final PoolingHttpClientConnectionManager connectionManager =
       new PoolingHttpClientConnectionManager();
   private final CloseableHttpClient hc;
   private int timeout;
 
+  private CommonsHttpClient(Builder builder) {
+    int timeoutSeconds = 300;
+    if (builder.databricksConfig != null
+        && builder.databricksConfig.getHttpTimeoutSeconds() != null) {
+      timeoutSeconds = builder.databricksConfig.getHttpTimeoutSeconds();
+    }
+    if (builder.timeoutSeconds != null) {
+      timeoutSeconds = builder.timeoutSeconds;
+    }
+    timeout = timeoutSeconds * 1000;
+    connectionManager.setMaxTotal(100);
+    HttpClientBuilder httpClientBuilder =
+        HttpClientBuilder.create()
+            .setConnectionManager(connectionManager)
+            .setDefaultRequestConfig(makeRequestConfig());
+    if (builder.proxyConfig != null) {
+      ProxyUtils.setupProxy(builder.proxyConfig, httpClientBuilder);
+    }
+    if (builder.sslSocketFactory != null) {
+      httpClientBuilder.setSSLSocketFactory(builder.sslSocketFactory);
+    }
+    hc = httpClientBuilder.build();
+  }
+
+  // These constructors have been deprecate in favour of a builder pattern.
+  // They will be removed in a future release.
+  @Deprecated
   public CommonsHttpClient(int timeoutSeconds) {
     timeout = timeoutSeconds * 1000;
     connectionManager.setMaxTotal(100);
     hc = makeClosableHttpClient();
   }
 
+  @Deprecated
   public CommonsHttpClient(DatabricksConfig databricksConfig) {
     this(
         databricksConfig.getHttpTimeoutSeconds() == null
@@ -56,6 +140,7 @@ public CommonsHttpClient(DatabricksConfig databricksConfig) {
         new ProxyConfig(databricksConfig));
   }
 
+  @Deprecated
   public CommonsHttpClient(int timeoutSeconds, ProxyConfig proxyConfig) {
     timeout = timeoutSeconds * 1000;
     connectionManager.setMaxTotal(100);
@@ -70,13 +155,15 @@ private RequestConfig makeRequestConfig() {
         .build();
   }
 
+  @Deprecated
   private CloseableHttpClient makeClosableHttpClient() {
     return HttpClientBuilder.create()
         .setConnectionManager(connectionManager)
         .setDefaultRequestConfig(makeRequestConfig())
         .build();
   }
 
+  @Deprecated
   private CloseableHttpClient makeClosableHttpClient(ProxyConfig proxyConfig) {
     HttpClientBuilder builder =
         HttpClientBuilder.create()

databricks-sdk-java/src/main/java/com/databricks/sdk/core/oauth/ClientCredentials.java

@@ -17,7 +17,7 @@ public static class Builder {
     private String clientId;
     private String clientSecret;
     private String tokenUrl;
-    private HttpClient hc = new CommonsHttpClient(30);
+    private HttpClient hc = new CommonsHttpClient.Builder().withTimeoutSeconds(30).build();
     private Map<String, String> endpointParams = Collections.emptyMap();
     private List<String> scopes = Collections.emptyList();
     private AuthParameterPosition position = AuthParameterPosition.BODY;

databricks-sdk-java/src/main/java/com/databricks/sdk/core/oauth/Consent.java

@@ -55,7 +55,7 @@ public class Consent implements Serializable {
   private final String clientSecret;
 
   public static class Builder {
-    private HttpClient hc = new CommonsHttpClient(30);
+    private HttpClient hc = new CommonsHttpClient.Builder().withTimeoutSeconds(30).build();
     private String authUrl;
     private String verifier;
     private String state;

databricks-sdk-java/src/test/java/com/databricks/sdk/core/commons/CommonsHttpClientTest.java

@@ -16,7 +16,7 @@ class CommonsHttpClientTest {
   @Test
   public void itWorks() throws IOException {
     try (FixtureServer fixtures = new FixtureServer().with("GET", "/foo?x=y", "bar")) {
-      HttpClient httpClient = new CommonsHttpClient(30);
+      HttpClient httpClient = new CommonsHttpClient.Builder().withTimeoutSeconds(30).build();
       Request in = new Request("GET", fixtures.getUrl() + "/foo").withQueryParam("x", "y");
       Response out = httpClient.execute(in);
       assertEquals("bar", out.getDebugBody().trim());
@@ -37,7 +37,7 @@ public void testStringBody() throws IOException {
             .withResponse("quux")
             .build();
     try (FixtureServer fixtures = new FixtureServer().with(fixture)) {
-      HttpClient httpClient = new CommonsHttpClient(30);
+      HttpClient httpClient = new CommonsHttpClient.Builder().withTimeoutSeconds(30).build();
       Request in = new Request("POST", fixtures.getUrl() + "/foo", "bar");
       Response out = httpClient.execute(in);
       assertEquals("quux", out.getDebugBody().trim());
@@ -58,7 +58,7 @@ public void testInputStreamBody() throws IOException {
             .withResponse("quux")
             .build();
     try (FixtureServer fixtures = new FixtureServer().with(fixture)) {
-      HttpClient httpClient = new CommonsHttpClient(30);
+      HttpClient httpClient = new CommonsHttpClient.Builder().withTimeoutSeconds(30).build();
       Request in =
           new Request("POST", fixtures.getUrl() + "/foo", IOUtils.toInputStream("bar", "UTF-8"));
       Response out = httpClient.execute(in);
@@ -76,7 +76,7 @@ public void testNoRedirection() throws IOException {
             .build();
 
     try (FixtureServer fixtures = new FixtureServer().with(fixture)) {
-      HttpClient httpClient = new CommonsHttpClient(30);
+      HttpClient httpClient = new CommonsHttpClient.Builder().withTimeoutSeconds(30).build();
       Request in = new Request("GET", fixtures.getUrl() + "/redirect");
       in.setRedirectionBehavior(
           false); // If we don't set redirection behavior to false, we get 200 as it gets
@@ -106,7 +106,7 @@ public void testRedirection() throws IOException {
                 .build());
 
     try (FixtureServer server = new FixtureServer().with(fixtures)) {
-      HttpClient httpClient = new CommonsHttpClient(30);
+      HttpClient httpClient = new CommonsHttpClient.Builder().withTimeoutSeconds(30).build();
       Request in = new Request("GET", server.getUrl() + "/redirect");
       Response out = httpClient.execute(in);
       assertEquals(

databricks-sdk-java/src/test/java/com/databricks/sdk/core/oauth/ExternalBrowserCredentialsProviderTest.java

@@ -35,7 +35,7 @@ void clientAndConsentTest() throws IOException {
               .setAuthType("external-browser")
               .setHost(fixtures.getUrl())
               .setClientId("test-client-id")
-              .setHttpClient(new CommonsHttpClient(30));
+              .setHttpClient(new CommonsHttpClient.Builder().withTimeoutSeconds(30).build());
       config.resolve();
 
       assertEquals("tokenEndPointFromServer", config.getOidcEndpoints().getTokenEndpoint());
@@ -70,7 +70,7 @@ void clientAndConsentTestWithCustomRedirectUrl() throws IOException {
               .setAuthType("external-browser")
               .setHost(fixtures.getUrl())
               .setClientId("test-client-id")
-              .setHttpClient(new CommonsHttpClient(30))
+              .setHttpClient(new CommonsHttpClient.Builder().withTimeoutSeconds(30).build())
               .setOAuthRedirectUrl("http://localhost:8010")
               .setScopes(Arrays.asList("sql"));
       config.resolve();
@@ -98,7 +98,7 @@ void openIDConnectEndPointsTestAccounts() throws IOException {
         new DatabricksConfig()
             .setAuthType("external-browser")
             .setHost("https://accounts.cloud.databricks.com")
-            .setHttpClient(new CommonsHttpClient(30))
+            .setHttpClient(new CommonsHttpClient.Builder().withTimeoutSeconds(30).build())
             .setAccountId("testAccountId");
     config.resolve();
 

examples/spring-boot-oauth-u2m-demo/src/main/java/com/databricks/sdk/App.java

@@ -20,7 +20,7 @@ public static void main(String[] args) {
 
     @Bean
     public HttpClient getHttpClient() {
-        return new CommonsHttpClient(30);
+        return new CommonsHttpClient.Builder().withTimeoutSeconds(30).build();
     }
 
     @Bean