deployer & gateway: added OpenAPI docs

[iulianbarbu]

Description of change

Added deployer & gateway OpenAPI spec. The raw openapi specs endpoints are scoped to Admin users that will be authorized through an API key. Example for gateway reachable on my localhost:

For gateway openapi spec:

curl -H "Authorization: Bearer test-key" localhost:8001/api-docs/openapi.json

For a specific project deployer:

curl -H "Authorization: Bearer test-key" localhost:8001/projects/{project_name}/api-docs/openapi.json (a specific project deployer docs).

How Has This Been Tested (if applicable)?

Generated the deployer & gateway open api specs and validated them here: https://editor.swagger.io/?_ga=2.66167150.1903807504.1681801827-1400620191.1681387801.

Disclaimer

1. The openapi docs can be improved by providing better APIs responses error documentation.
2. I can not manage yet to provide swagger UIs reachable through the gateway. For some reason, I get a 303 response from the gateway when I am trying to connect to the swagger-uis of both gateway/deployer. I think Chrome tries to follow the 303 redirect location but it ends up with a 404 not found. I need to investigate more on this but this PR is mergeable without the fix for swagger ui given they can be generated based on the openapi doc at: https://editor.swagger.io/?_ga=2.66167150.1903807504.1681801827-1400620191.1681387801.

[chesedo]

Nice, LGTM

[oddgrd]

LGTM, this is very cool, thanks @iulianbarbu!