Display a message to upgrade client if `minimumSupportedDesktopVersion` is thrown

[solracsf]

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Feature description

When minimumSupportedDesktopVersion is set, it simply throws a 403 for unsupported clients.
Instead, a clear message should be displayed on the client stating that

This version of client is unsupported by the server. Minimum supported version is "{minimumSupportedDesktopVersion}". Please, upgrade your client.

or similar. This is much more user friendly than a simple 403 Forbidden.

https://github.com/nextcloud/server/blob/9964bcbfd576e3c0627f9c6bc662b3168d12a80b/config/config.sample.php#L1991-L2004

https://github.com/nextcloud/server/blob/9964bcbfd576e3c0627f9c6bc662b3168d12a80b/apps/dav/lib/Connector/Sabre/BlockLegacyClientPlugin.php#L56-L75

[camilasan]

Desktop client PR: #6405
Server PR: nextcloud/server#43281