Made Parsec able to retry first db connection, cleaner docker-compose

[c4ffein]

No description provided.

[codecov]

Codecov Report

Merging #1258 into master will increase coverage by 18.18%.
The diff coverage is 69.23%.

@@             Coverage Diff             @@
##           master    #1258       +/-   ##
===========================================
+ Coverage   56.97%   75.15%   +18.18%     
===========================================
  Files         298      298               
  Lines       26291    26324       +33     
===========================================
+ Hits        14979    19785     +4806     
+ Misses      11312     6539     -4773     

Impacted Files	Coverage Δ
parsec/backend/postgresql/handler.py	77.08% <61.90%> (-3.54%)	⬇️
parsec/backend/cli/run.py	70.98% <100.00%> (+0.36%)	⬆️
parsec/backend/config.py	93.65% <100.00%> (+0.20%)	⬆️
parsec/backend/postgresql/factory.py	100.00% <100.00%> (ø)
parsec/core/gui/_resources_rc.py	80.00% <0.00%> (-1.25%)	⬇️
parsec/core/fs/remote_loader.py	84.75% <0.00%> (+0.44%)	⬆️
parsec/core/backend_connection/authenticated.py	96.93% <0.00%> (+0.51%)	⬆️
parsec/backend/postgresql/invite.py	96.36% <0.00%> (+0.60%)	⬆️
parsec/core/sync_monitor.py	92.01% <0.00%> (+1.26%)	⬆️
parsec/backend/client_context.py	95.89% <0.00%> (+1.36%)	⬆️
... and 80 more

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[touilleMan]

I think we could add a test on this pretty easily: just start the backend with a localhost:<dummy_port> (using unused_tcp_port fixture) as postgresql configuration, then check the number of warnings we endup with thanks to recwarn fixture (see https://docs.pytest.org/en/stable/warnings.html#recwarn)