feat: coverall; feat: coverall and github action badges; feat: rerout to redoc

[leehanchung]

Description

• added coverall into github actions pipeline.
• added coverall badge in README
• added github badges in README
• Reroutes to redoc instead of postman.

Type of change

Please delete options that are not relevant.

• 🎨 CSS Styling fix
• 🚑 Bug fix (non-breaking change which fixes an issue)
• ♻️ 🗑️ Re-factor, cleanup, un-comment, docstring
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)

Change Status

• 🏁 Complete, tested, ready to review and merge
• 🚥 Complete, but not tested (may need new tests)
• 🚧 WIP work-in-progress, PR is for discussion/feedback

How Has This Been Tested?

• Manually Functionality Testing
• Unit Test

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• There are no merge conflicts

[leehanchung]

Testing app is here:
https://ncov19-covid-coverall-zpzqskbw.herokuapp.com/