Added post data sanitising before passing to the external service.

Added user's capability check.
Few plugin API logic optimizing.
Added http curl setting script.
Added proper exception naming.

https://transfer.hft-stuttgart.de/gitlab/ulrike.pado/asyst-moodle-plugin/-/issues/4

api.php

@@ -113,4 +113,6 @@ function retry_api_request(client $apiclient, array $payload, int $maxretries =
             }
         }
     }
+
+    return false; // Return false if all retries fail.
 }