Until https://github.com/matrix-org/matrix-rust-sdk/pull/2862,
`GroupSessionManager::encrypt_session_for` called `Device::encrypt` (via
`Device::maybe_encrypt_room_key`.
`Device::encrypt` is a thin wrapper for `ReadOnlyDevice::encrypt`, but it also
has an `instrument` annotation.
https://github.com/matrix-org/matrix-rust-sdk/pull/2862 short-cuts
`Device::encrypt` and calls `ReadOnlyDevice::encrypt` directly: that was
functionally fine but of course means that we no longer benefit from the
`instrument` annotation.
This PR rectifies the situation by pushing the annotation down to
`ReadOnlyDevice::encrypt`. It also adds some documentation for that function,
since we are using it in more places now.
(Longer-term, I think we should probably aim to get rid of `Device::encrypt`
altogether, but that's a refactor I don't want to take on today.)
Richard van der Hoff
2aaa709b0e