Please add API documentation for the project

I could not find any document that describes how a client UI/ server can use the GCL. i.e. what is the format of the Search request, Select request etc. There is postman file, but tedious if all you want is to understand the API.
Please add doc/swagger documentation for the API exposed by Generic Client Layer

Start with the existing doc/swagger directory and the Postman file to identify the API exposed by the Generic Client Layer. Document the Search and Select request formats and the other exposed requests, with enough detail for a client UI or server to use them without relying on Postman; done means the API is described in doc/swagger.

Written by the indexing model from the issue text.