implement currentUser.toJSON() method

lib/modules/auth/user.js

@@ -74,11 +74,7 @@ export default class User {
     return this._valueOrNull('photoURL');
   }
 
-  get photoUrl() {
+  // TODO no RN android method yet, the SDK does have .getProviderData but returns as a List.
-    return this._valueOrNull('photoURL');
-  }
-
-  // TODO no android method yet, the SDK does have .getProviderData but returns as a List.
   // get providerData() {
   //   return this._valueOrNull('providerData');
   // }
@@ -101,6 +97,18 @@ export default class User {
    * METHODS
    */
 
+  toJSON() {
+    return {
+      uid: this.uid,
+      email: this.email,
+      emailVerified: this.emailVerified,
+      displayName: this.displayName,
+      providerId: this.providerId,
+      isAnonymous: this.isAnonymous,
+      photoURL: this.photoURL,
+    };
+  }
+
   delete(...args) {
     return this._auth.deleteUser(...args);
   }