Update a user in the cache, melding the new user into the existing one if it exists, or creating it if it doesn't.
If a channel context is passed, the function recurses with an empty context to update the user in the global cache as well.
The current PersistenceService.
The IRCUser to update.
The context to use as key to the cache section to update; may be a channel for a channel-specific update, or an empty string for a global update.
PersistenceService.channelUserCache
Update a user in the cache, melding the new user into the existing one if it exists, or creating it if it doesn't.
If a channel context is passed, the function recurses with an empty context to update the user in the global cache as well.