Makes setURL method on MLNImageSource public (#2197)

Co-authored-by: Bart Louwers <bart.louwers@gmail.com>

platform/darwin/src/MLNImageSource.h

@@ -81,6 +81,13 @@ MLN_EXPORT
  */
 @property (nonatomic, copy, nullable)NSURL *URL;
 
+/**
+ Sets the URL for the image source, performing necessary validations.
+
+ @param url The URL to set for the image source.
+ */
+- (void)setURL:(NSURL *)url;
+
 /**
  The source image.
 

platform/darwin/test/MLNImageSourceTests.m

@@ -39,4 +39,19 @@
     XCTAssertNil(source.URL);
 }
 
+- (void)testMLNImageSourceSetURL {
+    // Create a test instance of MLNImageSource
+    MLNCoordinateQuad quad = { { 80, 37}, { 81, 37}, { 81, 39}, { 80, 39}};
+    MLNImageSource *source = [[MLNImageSource alloc] initWithIdentifier:@"source-id" coordinateQuad:quad URL:[NSURL URLWithString:@"http://host/image.png"]];
+    
+    // Set the URL using setURL
+    NSURL *testURL = [NSURL URLWithString:@"http://host/image1.png"];
+    [source setURL:testURL];
+    
+    // Assert that the URL is set correctly
+    XCTAssertNotNil(source.URL);
+    XCTAssertEqualObjects(source.URL.absoluteString, @"http://host/image1.png");
+    XCTAssertNil(source.image);
+}
+
 @end