Deprecate, not remove, unused API (#10263)

Author: paulb777

FirebaseStorage/CHANGELOG.md

@@ -5,7 +5,7 @@
   `open func reference(forURL url: String) -> StorageReference` except it throws instead of
   erroring. (#6974)
 - [changed] The `FirebaseStorageInternal` CocoaPod has been discontinued.
-- [changed] Remove the `storageReference` property of `StorageMetadata`. It had never been implemented
+- [changed] Deprecate the `storageReference` property of `StorageMetadata`. It had never been implemented
   and always returned `nil`.
 - [changed] Storage APIs that previously threw an Objective-C exception now generate a Swift
   `fatalError`.

FirebaseStorage/Sources/StorageMetadata.swift

@@ -100,6 +100,11 @@ import Foundation
    */
   @objc public let updated: Date?
 
+  /**
+   * Never used API
+   */
+  @available(*, deprecated) @objc public let storageReference: StorageReference? = nil
+
   /**
    * Creates a Dictionary from the contents of the metadata.
    * @return A Dictionary that represents the contents of the metadata.

FirebaseStorage/Tests/ObjCIntegration/ObjCAPITests.m

@@ -169,6 +169,10 @@ - (void)FIRStorageMetadataApis {
   [metadata size];
   [metadata timeCreated];
   [metadata updated];
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+  [metadata storageReference];
+#pragma clang diagnostic pop
   FIRStorageMetadata __unused *ref2 = [metadata initWithDictionary:@{}];
   NSDictionary<NSString *, id> __unused *dict = [metadata dictionaryRepresentation];
   [metadata isFile];