Implemented token based authentication

[amlannandy]

Description

Login with react app doesn't persist the session in flask_login. So, we can return a auth token to the user on login. Which can be used in the Authorization header for accessing protected routes.

Fixes #84

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Try using a protected route without login, using the auth token in header.

Test Configuration:

• Chrome
• Postman
• Windows 10

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
• Any dependent changes have been merged and published in downstream modules