Provide remote configuration endpoint for easier setup

[juliushaertl]

Check with collabora to allow overloading of:

• [x] Alias groups
• [x] Font config endpoint https://github.com/CollaboraOnline/online/commit/3b6c531389087a1a7937c3b4df2861097d0ee17e
• [ ] Post allow list for previews
• [ ] Home edition flag

Documentation of the endpoint: https://sdk.collaboraonline.com/docs/installation/Configuration.html#dynamic-configuration

Once released

• [x] make sure that the collabora container has a environment variable for easy setup https://github.com/CollaboraOnline/online/commit/1ceb9784b027d6f027b4672686470d6522ec8593
• [ ] update documentation according to the new setup flow

[juliushaertl]

• [ ] Collabora could add a secret to access the convert-to
• [ ] We can provide the remote_config endpoint only with a shared secret which can then be added to the collabora config