This PR adds support (or is a proposal for) for supporting API KEY
authentication on the Llama Stack server end. `llama-stack-client`
already supports accepting an api_key parameter and passes it down
through every request as an `Authentication: ` header.
Currently, Llama Stack does not propose APIs for handling authentication
or authorization for resources of any kind. Given that, and the fact
that any deployment will typically have _some_ authentication system
present, we simply adopt a delegation mechanism: delegate to an HTTPS
endpoint performing key management / authentication.
It is configured via:
```yaml
server:
auth:
endpoint: <...>
```
in the run.yaml configuration.
## How It Works
When authentication is enabled:
1. Every API request must include an `Authorization: Bearer <token>`
header
2. The server will send a _POST_ validation request to the configured
endpoint with the following payload:
```json
{
"api_key": "<token>",
"request": {
"path": "/api/path",
"headers": { "header1": "value1", ... },
"params": { "param1": "value1", ... }
}
}
```
3. If the authentication endpoint returns a 200 status code, the request
is allowed to proceed
4. If the authentication endpoint returns any other status code, a 401
Unauthorized response is returned
## Test Plan
Unit tests
