Add identy check route leveraging API key and requestor IP for access

[samatstariongroup]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the COMET Web Services
• I have searched open and closed issues to ensure it has not already been reported

Description

Add a dedicated route that allows an identidy provider to authenticate a user agains the COMET database.

• implement GET request that uses username/password to validate user and return user info, including roles and permissions
• Implement GET request to assert whehter a user with a specific username exists, this will only return true or false and will not authenticate that user. This route needs to be rate limited (rate limitation needs to be configurable)
• protect route using an API keu
• only allow specific ip address to make the request

use policy based authentication to inplement - https://www.blogofpi.com/policy-based-authorization-in-asp-net-core/

this route will be used by external identity providers to perform authentication

• COMET Web Services version: net6/net7 version