Add API documentation

[k0malSharma]

Is your feature request related to a problem? Please describe.
For any newcomer, it can be difficult to grasp the operations taking place in the API

Describe the solution you'd like
An API documentation can help guide and give a better understanding of the API in the code

Describe alternatives you've considered
An API consisting of an introduction, overview of every model along with a clear explanation of all its functions