Gavin/115 create api endpoint stubs for recommender

[GDeane]

Description

This PR includes the stub methods/endpoints to implement for the recommender API.

Additionally, it includes some definitions of BaseModel classes which help to clearly define the allowed inputs and (successful response) outputs.

Closes #115

How to Test

1. Run 'docker-compose up --build' in the root of the martletplace repo.

2. Enter the following into your browser: http://localhost:8222/api/recommendations?authorization=spaghetti&page=1&limit=20

   • Your output should look like this:

3. Enter the following into your browser: http://localhost:8222/docs

   • The page should look like this:

4. For each endpoint shown, click 'try it out', fill out the parameter fields, and execute. Check the outputs.

Checklist

• [ ] The code includes tests if relevant
• [x] I have actually self-reviewed my changes and done QA