[SSE Sidecar] Authentication with Bearer Token

[RitaMAllenCA]

this requirement can be found in the following document:
https://docs.google.com/document/d/1vBRbBmij9HHotY_8HIaUKk5a9Kq9Rqgxlk-UAE_F7xs/edit#heading=h.95i1qjit3j6q

The RESTful endpoint should support basic authentication using an API bearer token.

curl --header "Authorization: Bearer : SIDECAR_API_KEY" http://127.0.0.1:18888/block

The API should return an Unauthorized error code if token is invalid.

HTTP/1.1 401 Unauthorized
Content-Type: application/json

{
  "error": {
    "message": "Unauthorized",
    "code": 401
  }
}