[Assessment] Product Quality - Coverage study

User story :
As Tympan team, I want to evaluate the portions of code that are tested, in order to identify those that need to be covered.

Acceptance criteria :

• Choice and implementation of the coverage tool (ex: "purecoverage")
• Evaluation of the coverage rate for all code parts (python, c++,...)
• Propose action plan with priority to optimize test coverage
• Complete testing section of readthedocs with coverage report (evaluation and action plan)