Event price can change after registration start
One-sentence description
Event price can change after registration start
Current behaviour / Reproducing the bug
- I register for an event accepting the costs etc
- The costs change
- I pay more than what I accepted
- I'm angry
😠 - Problems
Expected behaviour
Event prices cannot change after registration start!
This is also important for #632, since payments are made using the price in the event and if the price changes the payments cannot reflect that.