Support ETags for /ocs/v2.php/cloud/users/{userId} endpoint (or all ocs endpoints?)

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Is your feature request related to a problem? Please describe.
Motivation is to keep the transmitted data traffic from clients to the server as low as possible for 1. a better performance and 2. to preserve mobile traffic

Describe the solution you'd like
Support ETags in all ocs endpoints by default, but i will already be happy if this endpoint supports it:
/ocs/v2.php/cloud/users/{userId}

Describe alternatives you've considered
Not implementing human readable display names but technical user IDs because it's not worth the traffic without ETags in the Notes app.

Additional context
Some time ago someone already implemented this for the capabilities endpoint, maybe it's just a bit copy & paste...

cc @nickvergessen who pointed me here: https://github.com/nextcloud/notifications/blob/5ac74461141d8992bf1fb22c6e5fabf0544e5db1/lib/Controller/EndpointController.php#L128

Start by comparing the implementation referenced in notifications/lib/Controller/EndpointController.php around line 128 with the server OCS users endpoint at /ocs/v2.php/cloud/users/{userId}. Determine whether the change should cover that endpoint or all OCS endpoints; done means the selected endpoint(s) support ETags and avoid transmitting unchanged data.