Checks if the permission is granted on node If checkPermission on the permission.context is false, no permission is evaluated Does not handle the case that the user is an admin
Parameters
node
the node where the permission must be granted
permission
the permission to check for, none is checked if null
errorMessage
the message to throw in case the permission is not granted, appended to "User does not have permission to"
Throws
with the provided errorMessage in case the permission is not granted