Add REST API base implementation

[F-X64]

This PR adds a new structure to the project:
src/rhelocator/api/
Hosts the REST API server creation logic and configuration environment.

..api/routes
Hosts the individual endpoints for GCP, (AWS, Azure not implemented yet)

..api/schema
Hosts the individual swagger schema definitions for GCP, (AWS, Azure not implemented yet)

What is missing?

• AWS / Azure
• production build of REST server
• running the REST server in the entrypoint of the locator container

How to run the server:
poetry run rhelocator-updater serve --file-path

by default the server will start on 127.0.0.1:5000

API endpoints are reachable through
127.0.0.1:5000/api/gcp

Swagger documentation is available
http://127.0.0.1:5000/apidocs/

Notes:

• had to deactivate mypy test of untyped decorators.

Solves #14 , #96
Enables #47, #128, #129, #130, #131

[miyunari]

This looks really nice to me! Thank you for doing this :)