Changes to Get Endpoints Usage

added the optional property errors/items/source to the response with the 400 status

added the optional property errors/items/source to the response with the 401 status

added the optional property errors/items/source to the response with the 403 status

added the optional property errors/items/source to the response with the 429 status

added the optional property errors/items/source to the response with the 500 status

added the optional property errors/items/source to the response with the 504 status

the endpoint scheme security ApiKeyAuth was added to the API

the endpoint scheme security OAuth2 was added to the API

added the non-success response with the status 401