[Config] Split Codable APIs up and improve doc comments (#14552)

Author: ncooke3

FirebaseRemoteConfig/Swift/Codable.swift

@@ -44,11 +44,23 @@ public enum RemoteConfigCodableError: Error {
 }
 
 public extension RemoteConfig {
-  /// Decodes a struct from the respective Remote Config values.
+  /// Decodes the given type from the respective Remote Config values.
   ///
   /// - Parameter asType: The type to decode to.
+  /// - Throws: An error if the decoding fails.
+  /// - Returns: The decoded value; otherwise, an error if one occurred.
+  func decoded<Value: Decodable>(asType: Value.Type = Value.self) throws -> Value {
+    try decoded(asType: asType, decoder: FirebaseDataDecoder())
+  }
+
+  /// Decodes the given type from the respective Remote Config values.
+  /// - Parameters:
+  ///   - asType: The type to decode to.
+  ///   - decoder: The encoder to use to decode the given type.
+  /// - Throws: An error if the decoding fails.
+  /// - Returns: The decoded value; otherwise, an error if one occurred.
   func decoded<Value: Decodable>(asType: Value.Type = Value.self,
-                                 decoder: FirebaseDataDecoder = .init()) throws -> Value {
+                                 decoder: FirebaseDataDecoder) throws -> Value {
     let keys = allKeys(from: RemoteConfigSource.default) + allKeys(from: RemoteConfigSource.remote)
     let config = keys.reduce(into: [String: FirebaseRemoteConfigValueDecoderHelper]()) {
       $0[$1] = FirebaseRemoteConfigValueDecoderHelper(value: configValue(forKey: $1))
@@ -59,8 +71,18 @@ public extension RemoteConfig {
   /// Sets config defaults from an encodable struct.
   ///
   /// - Parameter value: The object to use to set the defaults.
+  /// - Throws: An error if the encoding fails.
+  func setDefaults<Value: Encodable>(from value: Value) throws {
+    try setDefaults(from: value, encoder: FirebaseDataEncoder())
+  }
+
+  /// Sets config defaults from an encodable struct.
+  /// - Parameters:
+  ///   - value: The object to use to set the defaults.
+  ///   - encoder: The encoder to use to encode the given object.
+  /// - Throws: An error if the encoding fails.
   func setDefaults<Value: Encodable>(from value: Value,
-                                     encoder: FirebaseDataEncoder = .init()) throws {
+                                     encoder: FirebaseDataEncoder) throws {
     guard let encoded = try encoder.encode(value) as? [String: NSObject] else {
       throw RemoteConfigCodableError.invalidSetDefaultsInput(
         "The setDefaults input: \(value), must be a Struct that encodes to a Dictionary"