#159327500 Create POST /auth/signup endpoint

[olusoladavid]

What does this PR do?

Adds an API endpoint to the app to help users create an account and the receive an authentication token

Description of Task to be completed

• Create SQL queries
• Create POST endpoint
• Validate user inputs
• Check for possible existing user
• Return JWT

How should this be manually tested?

• Pull branch into your local repo
• Run npm run dev in your local machine

Using Postman:
Send a POST request to /auth/signup with JSON body using the sample below:

{
"email": "validemail@gmail.com",
"password": "apassword"
}

What are the relevant pivotal tracker stories?

#159327500