Recursive REST API calls when connecting to the same environment in maintenance mode

[jensschuppe]

Steps to reproduce:

• Add a CiviMRF profile to connect to the same Drupal installation
• Enable the CiviMRF Views submodule
• Add a CiviMRF Views Dataset
• Enable maintenance mode
• Flush caches (e.g. via the "Flush cache" button on the Views Datasets configuration page
• (with a debugger, notice endless calls to the CiviCRM REST API endpoint)

This is due to the maintenance mode enabling a Drupal renderer routine that initializes the theme, which in turn calls the Views module's hook_views_data() implementations, including CiviMRF's that then tries to issue getfields calls to the CiviCRM API.

There should be some kind of a discovery mechanism before issueing an API call (or running the hook_views_data() implementation at all, when connecting to the same environment and the current request has been issued from this code. This would probably involve introducing signed requests (with a uuid).

[jensschuppe]

This might be mitigated by the API user needing permission to use the website in maintenance mode as otherwise those requests would be blocked before they can cause recursion.