#162693051 Create user registration API endpoint

[khwilo]

What does this PR do?

Create the API endpoint for user registration

Description of Task to be completed?

• Add tests for the user registration endpoint
• Add the logic for the user registration endpoint

How should this be manually tested?

Clone the repository and cd into it and run the command flask run on the terminal.

• Using Postman test the API endpoint /auth/signup using the following header:
  1. key - Content-Type
  2. value - application/json

What are the relevant pivotal tracker stories?

#162693051

Screenshots