Implement AuthN/AuthZ for Helium using AAD

[aka-msft]

Description

After Helium v1 is complete, update repository and add authentication and authorization to API endpoints.

Tasks

• Fork/update helium repo
• Establish requirements for groups and users that can access each Helium endpoint and verb (GET, POST, DELETE, etc.)
• Create groups + users in AAD (admin + regular users)
• Create a config file to map users to endpoints/verbs they're allowed access to
• Create middleware that checks if the user's token is valid and whether they have access to the endpoint/verb.
• Write tests for secured endpoints

Done

All Helium endpoints are secured with AAD, and tests are in place to verify security of endpoints.