Changes to Create Subscriptions for multiple Patients

the request property subscriptions became required

the request property subscriptions/items/type became required

the subscriptions request property's minItems was increased to 1

added the new optional request property subscriptions/items/monitoring_plan

added the optional property error_code to the response with the 400 status

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

added the optional property error_code to the response with the 404 status

added the optional property error_code to the response with the 406 status

added the optional property error_code to the response with the 500 status