Write Tests + Implement TDD

[DavidLemayian]

Is your feature request related to a problem? Please describe.
Currently we only do basic tests - security, deployment checks, and some unit tests.

Describe the solution you'd like
We should write more comprehensive unit tests and implement test driven development - where we write the tests first and then write the code.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.
TO DO

Additional context

Light reading on the same:

• https://medium.freecodecamp.org/isnt-tdd-test-driven-development-twice-the-work-why-should-you-care-4ddcabeb3df9
• https://medium.com/@solidi/8-observations-on-test-driven-development-a9b5144f868
• https://www.obeythetestinggoat.com/pages/book.html#toc
• https://www.youtube.com/watch?v=_rLPDxpXIFc

We'll also need the technologists to go through quick courses on how to do this well in Django.