Return $metadata resource as odata + openapi spec

Returning odata and openapi specs in json format.
Specs are scoped to the request permissions.
Different users (roles) will receive different metadata endpoints
and resources.

Change-type: minor
Signed-off-by: Harald Fischer <harald@balena.io>

Author: fisehara

openapiSpec.json

@@ -57,6 +57,7 @@
     "lodash": "^4.17.21",
     "memoizee": "^0.4.15",
     "pinejs-client-core": "^6.12.3",
+    "odata-openapi": "^0.19.1",
     "randomstring": "^1.2.3",
     "typed-error": "^3.2.2"
   },