Updating Ticket metadata

[kemurayama]

Is your feature request related to a problem? Please describe.
When I would like to add or update metadata for tickets, it seems Open Match doesn't have such methods for the purpose according to APIs. Users need to store updated metadata for matchmaking in other datastore.

Describe the solution you'd like
Let users to add or update ticket's metadata.

Describe alternatives you've considered
Use Redis store and store ticket ID and the updated data during the matchmaking.

Additional context
If Open Match assumes that ticket's properties are not updated during the matchmaking, I also would like to know it.