Don't send every DataMessage unsealed

[direc85]

@Schmiddiii writes in Whisperfish Matrix channel:

I have a question to #263: If I understand your code correctly, you take the unidentified_access on every single DataMessage here, which means try_send_message always gets None as unidentified access. Am I misunderstanding something? Shouldn't it be something like if end_session { unidentified_access.take() }?

I took a look at the code, and I arrived at the same conclusion, and developed a fix for the logic. So: the code previously made every DataMessage be sent identified/unsealed, whereas the intention is to use identified/unsealed sending for 1) EndSession messages and 2) messages to other own devices.

This has already received some real-world testing, and seems to work fine. As such, I was asked to make it a PR, so here it is!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2e3bd58) 3.65% compared to head (6821436) 3.65%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #268   +/-   ##
=====================================
  Coverage   3.65%   3.65%           
=====================================
  Files         38      38           
  Lines       2818    2818           
=====================================
  Hits         103     103           
  Misses      2715    2715           

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[gferon]

Thanks a lot for the fix!