Add support for deleting key

Author: ncooke3

FirebaseRemoteConfig/Swift/CustomSignals.swift

@@ -70,9 +70,9 @@ public extension RemoteConfig {
   /// Sets custom signals for this Remote Config instance.
   /// - Parameter customSignals: A dictionary mapping string keys to custom
   /// signals to be set for the app instance.
-  func setCustomSignals(_ customSignals: [String: CustomSignalValue]) async throws {
+  func setCustomSignals(_ customSignals: [String: CustomSignalValue?]) async throws {
     return try await withCheckedThrowingContinuation { continuation in
-      let customSignals = customSignals.mapValues { $0.toNSObject() }
+      let customSignals = customSignals.mapValues { $0?.toNSObject() ?? NSNull() }
       self.__setCustomSignals(customSignals) { error in
         if let error {
           continuation.resume(throwing: error)

FirebaseRemoteConfig/Tests/Swift/SwiftAPI/FirebaseRemoteConfigSwift_APIBuildTests.swift

@@ -225,12 +225,13 @@ final class FirebaseRemoteConfig_APIBuildTests: XCTestCase {
     let _: Void = try config.setDefaults(from: MyEncodableValue())
 
     Task {
-      let signals: [String: CustomSignalValue] = [
+      let signals: [String: CustomSignalValue?] = [
         "signal_1": .integer(5),
         "signal_2": .string("enable_feature"),
         "signal_3": 5,
         "signal_4": "enable_feature",
         "signal_5": "enable_feature_\("secret")",
+        "signal_6": nil, // Used to delete the custom signal for a given key.
       ]
       try await config.setCustomSignals(signals)
     }