feat: Add helm chart auth options.

[pantierra]

This PR adds the following authorization options to the helm chart:

stac-auth-proxy:
  enabled: true

  authorization:
  
    route:
      # mode: "default" (default, DEFAULT_PUBLIC), "custom", "private", "disabled"
      mode: "default"
     
      # Custom endpoint configurations (only used when mode: "custom")
      publicEndpoints: {}
        # Example:
        # "^/collections$": ["GET"]
        # "^/search$": ["GET", "POST"]
      privateEndpoints: {}
        # Example:
        # "^/collections$": [["POST", "collection:create"]]
        # "^/collections/([^/]+)/items$": [["POST", "item:create"]]
    
    record:
      # mode: "disabled" (default), "custom", "opa"
      mode: "disabled"
    
      # Custom filters configurations (only used when mode: "custom")
      custom:
        filtersFile: "data/custom_filters.py"
        
      # OPA configuration (only used when mode: "opa")
      opa:
        url: "http://opa:8181/"
        policy: "stac/items/allow"

Manual configuration via environment variables and manual mount of filter files is still possible.

The PR requires #114 and #117.

I open this as a draft, as I expect us to have a few iterations and conversations about this.

[alukach]

Should we push this into the docs directory to publish at developmentseed.org/stac-auth-proxy?

[pantierra]

This might be a bit out of context. We could move it into the docs but frame it as helm/kubernetes setup and include this.

[alukach]

Aside from the repo, is there anywhere else that this information would be surfaced?

I'd ideally like for people to be able to think about this tool as a packaged product rather than just a codebase, hence my view that docs should be available outside of the repo

[alukach]

Aside from the repo, is there anywhere else that this information would be surfaced?

I'd ideally like for people to be able to think about this tool as a packaged product rather than just a codebase, hence my view that docs should be available outside of the repo

[pantierra]

Happy to move it to the docs. Perhaps good to bring in #117 first? After that I can combine README and AUTHORIZATION into one file in the docs.

[alukach]

Will this (and the privateEndpoints) override the defaults established within the stac auth proxy's configuration?

[pantierra]

These would just set an env variable with the contents specified here. So, to my understanding, yes, if these are set, they will override them.

[pantierra]

Clarified a bit better in the comments.