Allow optional separate endpoint for query request on REST client plugin

Problem/Motivation

Some REST services might have different endpoints, this would allow the plugin to support these cases. For example:

Endpoint to fetch all objects: https://example.com/rest/service/query?f=json
Endpoint to fetch ONE objects: https://example.com/rest/service/1?f=json

Steps to reproduce

Proposed resolution

Allow for the configuration of more than one endpoint.

Remaining tasks

User interface changes

API changes

Data model changes