adding various utilities for thread channels in core
fixing enable feature not showing validation messages
restructuring feature mode collection to be a startup listener, because postconstruct might not have the appropriate values available, and therefore not initialize the map correctly
fixing editing a message without messages but only embeds not possible in channel service
refactoring closing parameters to use an object instead of parameters always
adding a progress indicator to closing a modmail thread
adding a notification to contact in order to show where the thread was created
fixing configuration for category (this caused the setup to fail, because there was no default value) and threadMessage feature modes not being correct
refactored model for closing header and added additional information
refactored modmail message logging to use the message history instead of individually loading the messages
adding nicer exception in case the mod mail message update failed
adding creation of AUserInAServer in case the user did not interact on the server yet
changed ID of modmail thread to be identical to the channel it was created in, this is so we can load the channel easier
not longer immediately instantiating the feature flag instance when a new server is found, but only when its config is changed or when a feature mod has its config changed
