[OPIK-121] Allow multiline in dataset description (#339)

* [OPIK-121] Allow multiline in dataset description

* Add docs

apps/opik-backend/src/main/java/com/comet/opik/utils/ValidationUtils.java

@@ -7,7 +7,25 @@
 
 public class ValidationUtils {
 
-    public static final String NULL_OR_NOT_BLANK = "^(?!\\s*$).+";
+    /**
+     * Regular expression to validate if a string is null or not blank.
+     *
+     * <p>It matches any string that is not null and contains at least one non-whitespace character.</p>
+     * For example:
+     * <ul>
+     *     <li>"" -> false</li>
+     *     <li>" " -> false</li>
+     *     <li>"\n" -> false</li>
+     *     <li>null -> true</li>
+     *     <li>"a" -> true</li>
+     *     <li>" a " -> true</li>
+     *     <li>"\n a \n" -> true</li>
+     * </ul>
+     *
+     * @see <a href="https://regexper.com/">Visual Explainer</a>
+     * @see <a href="https://zzzcode.ai/regex/explain">Ai Explainer</a>
+     */
+    public static final String NULL_OR_NOT_BLANK = "(?s)^\\s*(\\S.*\\S|\\S)\\s*$";
 
     /**
      * Canonical String representation to ensure precision over float or double.

apps/opik-backend/src/test/java/com/comet/opik/api/resources/v1/priv/DatasetsResourceTest.java

@@ -1197,6 +1197,22 @@ void create__success() {
             createAndAssert(dataset);
         }
 
+        @Test
+        @DisplayName("when description is multiline, then accept the request")
+        void create__whenDescriptionIsMultiline__thenAcceptTheRequest() {
+
+            var dataset = factory.manufacturePojo(Dataset.class).toBuilder()
+                    .id(null)
+                    .description("""
+                    Test
+                    Description
+                    """
+                    )
+                    .build();
+
+            createAndAssert(dataset);
+        }
+
         @Test
         @DisplayName("when creating datasets with same name in different workspaces, then accept the request")
         void create__whenCreatingDatasetsWithSameNameInDifferentWorkspaces__thenAcceptTheRequest() {

apps/opik-backend/src/test/java/com/comet/opik/api/resources/v1/priv/ProjectsResourceTest.java

@@ -854,6 +854,30 @@ void create__whenWorkspaceNameIsSpecified__thenAcceptTheRequest() {
             assertProject(project.toBuilder().id(id).build(), apiKey, workspaceName);
         }
 
+        @Test
+        @DisplayName("when workspace description is multiline, then accept the request")
+        void create__whenDescriptionIsMultiline__thenAcceptTheRequest() {
+            var project = factory.manufacturePojo(Project.class);
+
+            project = project.toBuilder().description("Test Project\n\nMultiline Description").build();
+
+            UUID id;
+            try (var actualResponse = client.target(URL_TEMPLATE.formatted(baseURI)).request()
+                    .accept(MediaType.APPLICATION_JSON_TYPE)
+                    .header(HttpHeaders.AUTHORIZATION, API_KEY)
+                    .header(WORKSPACE_HEADER, TEST_WORKSPACE)
+                    .post(Entity.json(project))) {
+
+                assertThat(actualResponse.getStatusInfo().getStatusCode()).isEqualTo(201);
+                assertThat(actualResponse.hasEntity()).isFalse();
+                assertThat(actualResponse.getHeaderString("Location")).matches(Pattern.compile(URL_PATTERN));
+
+                id = TestUtils.getIdFromLocation(actualResponse.getLocation());
+            }
+
+            assertProject(project.toBuilder().id(id).build());
+        }
+
         @Test
         @DisplayName("when description is null, then accept the request")
         void create__whenDescriptionIsNull__thenAcceptNameCreate() {

apps/opik-backend/src/test/java/com/comet/opik/utils/ValidationUtilsTest.java

@@ -0,0 +1,30 @@
+package com.comet.opik.utils;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ValidationUtilsTest {
+
+    public static Stream<Arguments> testNullOrNotBlank() {
+        return Stream.of(
+                Arguments.of("", false),
+                Arguments.of(" ", false),
+                Arguments.of("\n", false),
+                Arguments.of("a", true),
+                Arguments.of(" a ", true),
+                Arguments.of("\n a \n", true)
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource
+    void testNullOrNotBlank(String input, boolean expected) {
+        assertEquals(expected, input.matches(ValidationUtils.NULL_OR_NOT_BLANK));
+    }
+
+}