Add possibility to cancel or change in-game event registaration
An agent may want to cancel or change his/her event registration to other city. Currently this is not possible.
Possibility to cancel or change event place would make now even more sense since more events are now paid.
When an agent is cancelling event participation, it may not be cost efficient to give money back to agent, but giving event specific credit token to agent profile and possibility to use that credit token on later paid events may be good enough also.
For example when an agent cancels an Anomaly registration, one "free Anomaly" credit token is added to his/her agent profile. An agent may then use that token for Anomaly in other city or time.