ffi(bindings): check if MSC 4028 is enabled on the homeserver

[Velin92]

Added a function that returns true if the current homeserver has the msc 4028 push rule and is enabled.

Since I don't see Ruma having a specific push rule id for it yet, I am using an hardcoded string for now, is that okay?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5786b1a) 82.33% compared to head (85edfb5) 82.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2840      +/-   ##
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- Coverage   82.33%   82.33%   -0.01%     
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  Files         211      211              
  Lines       21620    21620              
==========================================
- Hits        17801    17800       -1     
- Misses       3819     3820       +1     

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[giomfo]

@Velin92 there is some ambiguity here.
The added function can_homeserver_push_encrypted_event_to_device doesn't check if the MSC4028 is enabled on the homeserver. It actually checks if the rule .m.rule.encrypted_event is present and enabled in the account push rules set.
This is a check at the account data level, not at the homeserver level.
This is true that this check gives you the information you need about the MSC4028 support server side, but it is ambiguous.

The right way to check the support of a feature server side is to used the _matrix/client/versions endpoint. But this MSC4028 is not considered for the moment by this endpoint.
I would be interested to sync with you to improve this, even if this is doing what you need

[giomfo]

Note: I just added msc4028 to the /_matrix/clients/versions endpoint at the spec level: matrix-org/matrix-spec-proposals@d3a1e87