Do not depend on buddy list entries when looking up the ID from the user name, by maintaining a bi-directional mapping ID <-> username. Rename functions to make them more evident as something that operatos on the lookup. Cleanup blist functions by implementating generic iterator function over account buddies.
Do not update blist buddy names, but set an alias instead to prevent breaking conversations or loosing history. Instead, keep the first print name as permanent user name
and set the alias on all buddy name changes. When interacting with purple always use the original buddy name stored in the blist instead of the print name provided by libpurple.
This allows both, meaningful names in group chats and permanent identifiers in the buddy list, while still propagating names changes to the interface.
Use print names instead of ids as usernames, to fix problems with "useless" user ids showing up for unknown users and in group chats. Remove workarounds like "Telegram Foreign" needed to temporarily store user names for alias resolution.
