Propagate max chunk size downstream to clients

[gymnae]

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Is your feature request related to a problem? Please describe.
If Nextcloud is behind a protective layer, for example Cloudflare, there is the need to set up chunking to enable the upload of files bigger than 100 MB.
Currently, this needs to be done manually in all locations which want to interact with the Nextcloud installation:

1. mobile clients
2. Server via OCC command
3. manual config file edit for Desktop clients

Especially the last part is a dealbreaker, since I cannot ask “simple” users to go and edit a config file stashed away somewhere and add a line, which I need to copy to them.

Describe the solution you'd like
The server should act as a central instance which can dictate the max size of chunks. Clients can manually opt for smaller chunks, but not bigger. The max chunk size is automatically stored in the config of the clients, without the need of them running into a 413 error and reducing the chunk size until it fits.

Describe alternatives you've considered
Hand tune every client installation by ensuring that they edit the config file or setting in the app. But, as pointed out, this solution doesn't scale.

There is at least this PR in the pipeline which could partly address the issue: nextcloud/desktop#4826

Additional context
Add any other context or screenshots about the feature request here.