chore: Add test for health handler

[thomaspoignant]

Description

Add test for health handler

Checklist

• I have tested this code
• I have added unit test to cover this code
• I have followed the contributing guide

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 33 lines in your changes missing coverage. Please review.

Project coverage is 3.94%. Comparing base (5eac14e) to head (8bcb3f2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
dao/inmemory_mock_impl.go	25.58%	32 Missing ⚠️
api/server.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main      #7      +/-   ##
========================================
+ Coverage   0.00%   3.94%   +3.94%     
========================================
  Files         12      13       +1     
  Lines        692     735      +43     
========================================
+ Hits           0      29      +29     
- Misses       692     706      +14     

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