v2 - tags present in operation but in global tags object should be valid #2364
Description
If a document has a tag in an operation that does NOT have a matching entry in the global tags object, it should be considered valid and parse/serialize accordingly.
Today parsing such document results in an error. So does serializing one.
If a tag in operations (which relies on the references infrastructure) does not have a matching entry in the global object during serialization, we should simply serialize the "reference id".