Provide the OnlyOffice desktop cloud URL

[Facyla]

OnlyOffice lets user users use their local desktop editor to edit files. Edited files are synced with the online file, implement a lock system and support both collaboration modes that are available in online editor.
For this feature to be usable, one need to provide the OnlyOffice server url, and then be able to login into against that endpoint:

Is your feature request related to a problem? Please describe.
The ability to use the onlyoffice desktop editor, and in general whatever editor a user prefers.

Describe the solution you'd like
The ability to connect desktop editors, at least OnlyOffice, and (why not) also LibreOffice.

Describe alternatives you've considered
This is not as essential as the ability to work offline and sync changes afterwards, but still would be very nice to have, as it foster the versatility and openness of the platform.