Rework rpc server

[BenediktBurger]

Some ideas from #100 and preparation for expansion.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.94%. Comparing base (54bda60) to head (003def0).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #102      +/-   ##
==========================================
+ Coverage   89.52%   89.94%   +0.42%     
==========================================
  Files          38       38              
  Lines        2988     2994       +6     
  Branches      312      310       -2     
==========================================
+ Hits         2675     2693      +18     
+ Misses        262      255       -7     
+ Partials       51       46       -5     

Flag	Coverage Δ
unittests	89.94% <100.00%> (+0.42%)	⬆️

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