[Backend API] Add internal auth

[justinyoo]

AS a logged in user
I WANT make API calls to API app with my auth details
SO THAT I can populate UI related data on the screen

[justinyoo]

• Pass pre-defined API key from web app to api app

[justinyoo]

Not relevant

[justinyoo]

Only for internal auth - admin related API requests

[justinyoo]

1. [OpenAPI] Add security auth #174
2. [Backend API] Interface design for internal auth #175
3. [Backend API] Implementation for internal auth #176
4. [Playground] Component for auth (UI only) #177
5. [Playground] Component for auth (UI logic only) #223