Improve makefile and run tests in parallel

[rameshsunkara]

• Update make file to improve readability
• Run tests in parallel to speed up execution
• Use table driven test cases in all tests

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 87.82%. Comparing base (5079d0f) to head (62a5d0e).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/db/ordersRepo.go	57.14%	2 Missing and 1 partial ⚠️
internal/db/mocks/orders.repo_mock.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #35      +/-   ##
==========================================
+ Coverage   85.86%   87.82%   +1.95%     
==========================================
  Files          18       18              
  Lines         658      805     +147     
==========================================
+ Hits          565      707     +142     
- Misses         78       92      +14     
+ Partials       15        6       -9     

Flag	Coverage Δ
unittests	87.82% <50.00%> (+1.95%)	⬆️

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