Headless signup user metadata option (#69)

* headless signup user metadata option

* Improve extraMetadata and metadataFields documentation

* Add trailing comma

---------

Co-authored-by: dshukertjr <dshukertjr@gmail.com>

Author: tomasAlabes

lib/src/components/supa_email_auth.dart

@@ -67,13 +67,18 @@ class SupaEmailAuth extends StatefulWidget {
   /// Callback for sending the password reset email
   final void Function()? onPasswordResetEmailSent;
 
-  /// Callback for when the auth action threw an excepction
+  /// Callback for when the auth action threw an exception
   ///
   /// If set to `null`, a snack bar with error color will show up.
   final void Function(Object error)? onError;
 
+  /// Set of additional fields to the signup form that will become
+  /// part of the user_metadata
   final List<MetaDataField>? metadataFields;
 
+  /// Additional properties for user_metadata on signup
+  final Map<String, dynamic>? extraMetadata;
+
   /// {@macro supa_email_auth}
   const SupaEmailAuth({
     Key? key,
@@ -83,6 +88,7 @@ class SupaEmailAuth extends StatefulWidget {
     this.onPasswordResetEmailSent,
     this.onError,
     this.metadataFields,
+    this.extraMetadata,
   }) : super(key: key);
 
   @override
@@ -204,11 +210,7 @@ class _SupaEmailAuthState extends State<SupaEmailAuth> {
                       email: _emailController.text.trim(),
                       password: _passwordController.text.trim(),
                       emailRedirectTo: widget.redirectTo,
-                      data: widget.metadataFields == null
-                          ? null
-                          : _metadataControllers.map<String, dynamic>(
-                              (metaDataField, controller) =>
-                                  MapEntry(metaDataField.key, controller.text)),
+                      data: _resolveData(),
                     );
                     widget.onSignUpComplete.call(response);
                   }
@@ -295,4 +297,23 @@ class _SupaEmailAuthState extends State<SupaEmailAuth> {
       ),
     );
   }
+
+  /// Resolve the user_metadata that we will send during sign-up
+  ///
+  /// In case both MetadataFields and extraMetadata have the same
+  /// key in their map, the MetadataFields (form fields) win
+  Map<String, dynamic> _resolveData() {
+    var extra = widget.extraMetadata ?? <String, dynamic>{};
+    extra.addAll(_resolveMetadataFieldsData());
+    return extra;
+  }
+
+  /// Resolve the user_metadata coming from the metadataFields
+  Map<String, dynamic> _resolveMetadataFieldsData() {
+    return widget.metadataFields != null
+        ? _metadataControllers.map<String, dynamic>(
+            (metaDataField, controller) =>
+                MapEntry(metaDataField.key, controller.text))
+        : <String, dynamic>{};
+  }
 }