Immovable flags are flags that cannot be picked up by players/vehicles. They remain where they are and, upon being touched, the ownership of the flag is typically assigned to the team that touched it.
Note that the logic around flag ownership can and should be done in the game script rather than in the Zone Server core logic, in case we want to have different things happen once it is touched.
Once it has been updated however, it's updated information needs to be sent out to the clients.
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