[docs] - Swagger Open API documentation

### Description

To enable end users/API consumers know available endpoints, relevant parameters, valid data and their types, url and request methods we need a documentation for the API.

This API documentation will be generated using swagger tools, particularly `swagger-jsdoc` and `swagger-ui-express` and will be hosted on /api-docs. Alternative API documentation tools can be used.

- https://github.com/scottie1984/swagger-ui-express
- https://github.com/Surnet/swagger-jsdoc

**Support Articles:**
- https://itnext.io/setting-up-swagger-in-a-node-js-application-d3c4d7aa56d4
- https://medium.com/@dlowkeen/auto-generating-swagger-documentation-for-your-node-api-c806cedbdd3e

Start by reviewing the API endpoints and the swagger-jsdoc and swagger-ui-express guidance linked in the issue. Document available endpoints, parameters, valid data and types, URLs, and request methods, then make the generated documentation available at /api-docs.

Written by the indexing model from the issue text.