Chat unavailable error messages changed

[pietroalbini]

I noticed Telegram changed some error messages for unavailable chats.

• deleted user became user is deleted
• chat deactivated became chat is migrated
• PEER_ID_INVALID means Telegram can't relate the chat to your bot, which should be marked as "not_found"

Those should be updated in botogram.

[pietroalbini]

I'm awaiting confirmation from the Bot Support about this.

[pietroalbini]

Also found that "chat deactivated" became "chat is migrated"...

[pietroalbini]

Got another little chat with the bot support. PEER_ID_INVALID is when Telegram can't find the relation with the chat and the bot, so I'll mark that as "not_found".