Problem with UserDefinedAction in Init Section

Describe the feature

Currently it is not possible to use UserDefinedAction in the Init section and have the action assigned to a specific actor.

The reason is that for PrivateAction the actor is specified in the parental Private element, where Private can only be used in the Init section. There is no equivalent for UserDefinedAction.

Describe the solution you would like

A possible solution might be to add a new element similar to Private for UserDefinedAction that is only usable in Init. Additionally we should disallow old usage of UserDefinedAction in init section. This breaks backward compatibility.

Describe alternatives you have considered

Could not think of anything else. Adding the entityRef to UserDefinedAction does not seem a good solution, as actors are specified in the Actors element of ManeuverGroup.

Describe the backwards compatibility

Might break backward compatibility, depending on the implementation.

Additional context

The example shows the difference between UserDefinedAction and PrivateAction.

<Actions>
	<UserDefinedAction>
		<CustomCommandAction type='{"Custom_Parameter" : true}'/>
	</UserDefinedAction>
	<Private entityRef="F0: F0">
		<PrivateAction>
			<TeleportAction>
				<Position>
					<WorldPosition x="501" y="4.5" z="0" h="4.71" p="0" r="0"/>
				</Position>
			</TeleportAction>
		</PrivateAction>
	</Private>
</Actions>