Changes to Upgrades and downgrades

added UpstreamErrorResponse subschema #2 to the response body oneOf list for the response status 503

the response's body type changed from object to no type for status 503

removed the required property error from the response with the 503 status

removed the optional property code from the response with the 503 status

removed the optional property detail from the response with the 503 status

removed the optional property hint from the response with the 503 status

removed the optional property plan from the response with the 503 status

removed the optional property reason from the response with the 503 status

added the non-success response with the status 500

added the non-success response with the status 502

added the non-success response with the status 504

added the optional property meta/stale_since to the response with the 200 status

added the optional property meta/data_age_days to the response with the 200 status

added the optional property meta/notes to the response with the 200 status

added the optional property meta/period to the response with the 200 status

the response property data/items/action became optional for the status 200

the response property data/items/date became optional for the status 200

the response property data/items/firm became optional for the status 200

the response property data/items/from_grade became optional for the status 200

the response property data/items/to_grade became optional for the status 200

response property data/items/action list-of-types was widened by adding types null to media type application/json of response 200

response property data/items/date list-of-types was widened by adding types null to media type application/json of response 200

response property data/items/firm list-of-types was widened by adding types null to media type application/json of response 200

response property data/items/from_grade list-of-types was widened by adding types null to media type application/json of response 200

response property data/items/to_grade list-of-types was widened by adding types null to media type application/json of response 200

added the optional property code to the response with the 401 status

added the optional property code to the response with the 429 status

added the optional property code to the response with the 503 status

added the optional property hint to the response with the 401 status

added the optional property hint to the response with the 429 status

added the optional property hint to the response with the 503 status

added the optional property plan to the response with the 401 status

added the optional property plan to the response with the 429 status

added the optional property plan to the response with the 503 status

added the optional property reason to the response with the 401 status

added the optional property reason to the response with the 429 status

added the optional property reason to the response with the 503 status