feat(auth): add documentation

packages/firebase_auth/firebase_auth/lib/src/multi_factor.dart

@@ -54,6 +54,8 @@ class PhoneMultiFactorGenerator {
   }
 }
 
+/// Represents an assertion that the Firebase Authentication server
+/// can use to authenticate a user as part of a multi-factor flow.
 class MultiFactorAssertion {
   final MultiFactorAssertionPlatform _delegate;
 
@@ -62,6 +64,8 @@ class MultiFactorAssertion {
   }
 }
 
+/// Utility class that contains methods to resolve second factor
+/// requirements on users that have opted into two-factor authentication.
 class MultiFactorResolver {
   final FirebaseAuth _auth;
   final MultiFactorResolverPlatform _delegate;
@@ -87,6 +91,8 @@ class MultiFactorResolver {
   }
 }
 
+/// MultiFactor exception related to Firebase Authentication. Check the error code
+/// and message for more details.
 class FirebaseAuthMultiFactorException extends FirebaseAuthException {
   final FirebaseAuth _auth;
   final FirebaseAuthMultiFactorExceptionPlatform _delegate;

packages/firebase_auth/firebase_auth_platform_interface/lib/src/platform_interface/platform_interface_multi_factor.dart

@@ -56,10 +56,12 @@ class MultiFactorSession {
   final String id;
 }
 
+/// {@template .multiFactorAssertion}
 /// Represents an assertion that the Firebase Authentication server
 /// can use to authenticate a user as part of a multi-factor flow.
+/// {@endtemplate}
 class MultiFactorAssertionPlatform extends PlatformInterface {
-  /// {@macro .platformInterfaceMultiFactor}
+  /// {@macro .multiFactorAssertion}
   MultiFactorAssertionPlatform() : super(token: _token);
 
   static final Object _token = Object();
@@ -70,7 +72,7 @@ class MultiFactorAssertionPlatform extends PlatformInterface {
   }
 }
 
-/// {@macro .platformInterfaceMultiFactorResolverPlatform}
+/// {@template .platformInterfaceMultiFactorResolverPlatform}
 /// Utility class that contains methods to resolve second factor
 /// requirements on users that have opted into two-factor authentication.
 /// {@endtemplate}