#162497556 implements api to create intervention record

[valenstical]

What does this PR do? This PR sets up endpoint to create new intervention record

Description of tasks

• Implement unit test for the endpoint
• Setup API endpoint for POST /api/v1/interventions/ and make sure all tests are passing

How can this PR be tested

• Using Postman, set the request method to POST
• Make requests to https://ireporter-nigeria.herokuapp.com/api/v1/interventions/

What are the relevant pivotal tracker stories? #162497556

Screenshot N/A