feat(auth, web): add SAMLProvider support to Web (#10075)

Author: Lyokone

packages/firebase_auth/firebase_auth_web/lib/src/interop/auth.dart

@@ -963,6 +963,26 @@ class TwitterAuthProvider
       auth_interop.TwitterAuthProviderJsImpl.credential(token, secret);
 }
 
+/// SAML auth provider.
+///
+/// See: <https://firebase.google.com/docs/reference/js/auth.samlauthprovider>.
+class SAMLAuthProvider
+    extends AuthProvider<auth_interop.SAMLAuthProviderJsImpl> {
+  /// Creates a new SAMLAuthProvider with the providerId.
+  /// The providerId must start with "saml."
+  factory SAMLAuthProvider(String providerId) => SAMLAuthProvider.fromJsObject(
+      auth_interop.SAMLAuthProviderJsImpl(providerId));
+
+  /// Creates a new SAMLAuthProvider from a [jsObject].
+  SAMLAuthProvider.fromJsObject(auth_interop.SAMLAuthProviderJsImpl jsObject)
+      : super.fromJsObject(jsObject);
+
+  /// Used to extract the underlying OAuthCredential from a UserCredential.
+  static auth_interop.OAuthCredential? credentialFromResult(
+          auth_interop.UserCredentialJsImpl userCredential) =>
+      auth_interop.SAMLAuthProviderJsImpl.credentialFromResult(userCredential);
+}
+
 /// Phone number auth provider.
 ///
 /// See: <https://firebase.google.com/docs/reference/js/firebase.auth.PhoneAuthProvider>.

packages/firebase_auth/firebase_auth_web/lib/src/interop/auth_interop.dart

@@ -471,6 +471,14 @@ class PhoneAuthProviderJsImpl extends AuthProviderJsImpl {
   );
 }
 
+@JS('SAMLAuthProvider')
+class SAMLAuthProviderJsImpl extends AuthProviderJsImpl {
+  external factory SAMLAuthProviderJsImpl(String providerId);
+  external static OAuthCredential? credentialFromResult(
+    UserCredentialJsImpl userCredential,
+  );
+}
+
 @JS('ApplicationVerifier')
 abstract class ApplicationVerifierJsImpl {
   external String get type;

packages/firebase_auth/firebase_auth_web/lib/src/utils/web_utils.dart

@@ -261,6 +261,10 @@ auth_interop.AuthProvider convertPlatformAuthProvider(
     return oAuthProvider;
   }
 
+  if (authProvider is SAMLAuthProvider) {
+    return auth_interop.SAMLAuthProvider(authProvider.providerId);
+  }
+
   throw FallThroughError();
 }