Pagination for submitting responses to central instance

[davidszkiba]

Note: this is based on work done in issue #723 and the corresponding branch dev-david-issue-723

The problem: when there are too many response data to be submitted to the central instance, the client sending those data can run out of memory.

At the moment, sending responses works like this:

• Go to the catquiz manager, go to the CAT scales tab, click "View" on the root scale (simulation) and on the resulting page, click "submit responses to hub"
• This triggers an AJAX call to a webservice that is running on the local instance
• In this webservice, we call the response_submitter class, which gets all required data and sends them to the central instance (see https://github.com/Wunderbyte-GmbH/moodle-local_catquiz/blob/dev-david-issue-723/classes/remote/client/response_submitter.php#L73)

Solution would be to send the response data in batches of e.g. 1000 responses per request.
This means:

• Update the catquiz::get_sql_for_model_input() function to take additional parameters to support pagination.
• Instead of directly sending the data, create a new adhoc task for each batch and send the data in the adhoc task
• Continue with the next batch
  @georgmaisser knows how this can be done