[O2B-677] Add documentation

[martinboulais]

I DON'T have JIRA ticket

• [x] explain what this PR does
• [x] documentation was updated or added

Notable changes for developers:

• A general architecture documentation has been added

[codecov[bot]]

Codecov Report

Merging #784 (3139663) into main (f72c2ff) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #784   +/-   ##
=======================================
  Coverage   47.56%   47.56%           
=======================================
  Files         448      448           
  Lines        7035     7035           
  Branches     1320     1320           
=======================================
  Hits         3346     3346           
  Misses       3689     3689           

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