feat: provider support jwt authentication

[Gilles-Marco]

Description of my issue / environment

I don't use the litellm master key to authenticate to my litellm instance.

I authenticate against an identity provider, giving me an JWT that it used as the api_token.

This IdP token can be read, validated and give me admin permission to my litellm instance.

The change I made

The change adds attributes to the litellm provider and make optionnal the api token.
These added attributes are used to do an HTTP Post request against the identity provider to get an access token
And this access token is then passed as the api_token.

I let the attribute request_header and request_payload widly configurable because depending on the IdP the request payload and header are not the same, to retrieve an access_token.

Example litellm terraform provider

provider "litellm"{
  
  jwt_token_endpoint = "https://<my-identity-provider-hostname>/token"
  jwt_request_header = {
    "Content-Type" = "application/x-www-form-urlencoded"
  }
  jwt_request_payload = {
    client_id = "<Client ID registered in the IdP>"
    client_secret = "<Client secret given by the IdP when the client was registered>"
    scope = "<scope used by litellm to identity the token as admin>"
    grant_type = "client_credentials" 
  }
  api_base_url = "https://<my-litellm-api-base-endpoint>"
}

I tested it, I created an example model and it worked.

To replicate my environment you could use keykloak

[gzamboni]

Awesome work! Ty so much.
There is only one problem here, there is no terraform documentation for all new things you implemented, hashicorp requires documentation that follows their standards.
You can see in /docs, /examples and https://developer.hashicorp.com/terraform/registry/providers/docs

without this, we cannot publish this code in the terraform official registry

[Gilles-Marco]

Hello, thanks you for the review.

I started to work on the documentation of my works.

I moved the existing documentation to /templates and templatize it because when running tfplugindocs generate it overwrote your's manually written content.

[Gilles-Marco]

Done adding the example and description for each PR i had done. Let me know if you want more details on some parts.