Add lookup endpoint to api spec

[mattoni]

Adds support for resource identifier string lookups:

/v1/utils/lookup?identifier=<base64-resource-identifier>&desired-component=<string>

• Where identifier is a base-64'd resource identifier string. For example: cluster:production/environment:654d4e848924c1c445c3635a/container:api or cntr:api/env:production/clst:production
• desired-component is the type of resource you want to pull the ID for.

This endpoint will return a response in the shape of:

{
  "data": {
    "id": <id>
  }
}