Implement MSC3987, fix setting Element Android notifications

[S7evinK]

Should fix #3183, since Element Android already implements MSC3987

This is also part of #3225

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (8b3adaf) 65.13% compared to head (13da5c3) 65.99%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3242      +/-   ##
==========================================
+ Coverage   65.13%   65.99%   +0.86%     
==========================================
  Files         507      507              
  Lines       57174    57173       -1     
==========================================
+ Hits        37240    37732     +492     
+ Misses      16031    15659     -372     
+ Partials     3903     3782     -121     

Flag	Coverage Δ
unittests	49.48% <75.00%> (+0.04%)	⬆️

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Files	Coverage Δ
internal/pushrules/default_override.go	100.00% <100.00%> (ø)
internal/pushrules/validate.go	100.00% <100.00%> (ø)
userapi/consumers/roomserver.go	71.13% <100.00%> (+0.94%)	⬆️
internal/pushrules/util.go	91.35% <0.00%> (-1.42%)	⬇️

... and 74 files with indirect coverage changes

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