feat: Add feature metadata tests (#31)

Author: khvn26

test_cases/test_feature_override_with_metadata__match__metadata_in_result.jsonc

@@ -0,0 +1,80 @@
+{
+  // Given: A feature with metadata, a segment overriding it and
+  //        including own feature metadata, and an identity matching the segment
+  // When: A context is evaluated
+  // Then: The result should include the feature metadata from the override
+  "$schema": "https://raw.githubusercontent.com/Flagsmith/engine-test-data/refs/tags/v2.0.0/schema.json",
+  "context": {
+    "environment": {
+      "key": "key",
+      "name": "Environment"
+    },
+    "identity": {
+      "identifier": "metadata_user",
+      "key": "key_metadata_user"
+    },
+    "features": {
+      "feature_with_metadata": {
+        "enabled": true,
+        "feature_key": "12345",
+        "key": "1",
+        "name": "feature_with_metadata",
+        "value": null,
+        "metadata": {
+          "source": "imported"
+        }
+      }
+    },
+    "segments": {
+      "1": {
+        "key": "1",
+        "name": "segment",
+        "rules": [
+          {
+            "type": "ALL",
+            "conditions": [
+              {
+                "operator": "EQUAL",
+                "property": "$.identity.identifier",
+                "value": "metadata_user"
+              }
+            ]
+          }
+        ],
+        "overrides": [
+          {
+            "enabled": false,
+            "feature_key": "12345",
+            "feature": "feature_with_metadata",
+            "key": "1",
+            "name": "feature_with_metadata",
+            "value": "overridden",
+            "metadata": {
+              "source": "overridden"
+            }
+          }
+        ]
+      }
+    }
+  },
+  "result": {
+    "flags": {
+      "feature_with_metadata": {
+        "enabled": false,
+        "feature_key": "12345",
+        "name": "feature_with_metadata",
+        "reason": "TARGETING_MATCH; segment=segment",
+        "value": "overridden",
+        "metadata": {
+          "source": "overridden"
+        }
+      }
+    },
+    "segments": [
+      {
+        "key": "1",
+        "name": "segment"
+      }
+    ]
+  }
+}

test_cases/test_feature_with_metadata__metadata_in_result.jsonc

@@ -0,0 +1,39 @@
+{
+  // Given: A feature with metadata
+  // When: A context is evaluated
+  // Then: The result should include the feature metadata
+  "$schema": "https://raw.githubusercontent.com/Flagsmith/engine-test-data/refs/tags/v2.0.0/schema.json",
+  "context": {
+    "environment": {
+      "key": "key",
+      "name": "Environment"
+    },
+    "features": {
+      "feature_with_metadata": {
+        "enabled": true,
+        "feature_key": "12345",
+        "key": "1",
+        "name": "feature_with_metadata",
+        "value": null,
+        "metadata": {
+          "source": "imported"
+        }
+      }
+    }
+  },
+  "result": {
+    "flags": {
+      "feature_with_metadata": {
+        "enabled": true,
+        "feature_key": "12345",
+        "name": "feature_with_metadata",
+        "reason": "DEFAULT",
+        "value": null,
+        "metadata": {
+          "source": "imported"
+        }
+      }
+    },
+    "segments": []
+  }
+}