Added API server to request shutdown

[marcoSanti]

Added an API server to manage the termination of the CAPIO server instance. The APIs available are:

• GET / -> return identity of capio_server
• GET /clients -> return count of connected clients
• GET /terminate -> Requests a graceful termination phase.

[codecov]

Codecov Report

❌ Patch coverage is 33.89831% with 39 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.45%. Comparing base (e488e38) to head (f561cf1).
⚠️ Report is 1 commits behind head on capio-v2.

Files with missing lines	Patch %	Lines
capio-server/include/api-server/api-server.hpp	0.00%	10 Missing and 8 partials ⚠️
capio-server/src/api-server/api-server.cpp	37.93%	4 Missing and 14 partials ⚠️
capio-server/include/utils/signals.hpp	72.72%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           capio-v2     #166      +/-   ##
============================================
- Coverage     42.58%   42.45%   -0.14%     
============================================
  Files            82       84       +2     
  Lines          4567     4612      +45     
  Branches       2712     2745      +33     
============================================
+ Hits           1945     1958      +13     
- Misses         1328     1337       +9     
- Partials       1294     1317      +23     

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