refactor: direct method to init DatafileContent from JSONString

Sources/FeaturevisorSDK/Instance.swift

@@ -258,14 +258,17 @@ public class FeaturevisorInstance {
     }
 
     func setDatafile(_ datafileJSON: String) {
-
-        guard let data = datafileJSON.data(using: .utf8) else {
-            logger.error("could not get datafile as data representation")
-            return
-        }
-
         do {
-            let datafileContent = try JSONDecoder().decode(DatafileContent.self, from: data)
+            let datafileContent = try DatafileContent.from(string: datafileJSON)
+
+            guard let datafileContent else {
+                logger.error(
+                    "could not get datafile as data representation",
+                    ["jsonDatafile": datafileJSON]
+                )
+                return
+            }
+
             datafileReader = DatafileReader(datafileContent: datafileContent)
         }
         catch {

Sources/FeaturevisorTypes/Extensions/DatafileContent+Init.swift

@@ -0,0 +1,13 @@
+import Foundation
+
+extension DatafileContent {
+
+    public static func from(string datafileJSONString: String) throws -> DatafileContent? {
+
+        guard let data = datafileJSONString.data(using: .utf8) else {
+            return nil
+        }
+
+        return try JSONDecoder().decode(DatafileContent.self, from: data)
+    }
+}

Tests/FeaturevisorTypesTests/FeaturevisorTypesTests.swift

@@ -15,7 +15,7 @@ final class FeaturevisorTypesTests: XCTestCase {
 
         // WHEN
         let json = try Data(contentsOf: path)
-        let result = try JSONDecoder().decode(DatafileContent.self, from: json)
+        let result = try DatafileContent.from(string: String(decoding: json, as: UTF8.self))!
 
         // THEN
         XCTAssertEqual(result.revision, "0.0.13")