Allow access token to be retrieved using post data

Author: ricog

src/Middleware/SocialAuthMiddleware.php

@@ -356,7 +356,9 @@ protected function _getSocialIdentity($providerName, ServerRequest $request): ?a
     {
         try {
             $provider = $this->_getService($request)->getProvider($providerName);
-            $accessToken = $provider->getAccessTokenByRequestParameters($request->getQueryParams());
+            $queryParams = $request->getQueryParams();
+            $data = !empty($queryParams) ? $queryParams : $request->getData();
+            $accessToken = $provider->getAccessTokenByRequestParameters($data);
             $identity = $provider->getIdentity($accessToken);
 
             if (!$identity->id) {