This regression happened in bd5c5c4b5f and is due to `message_bus_targets = calculate_publish_targets(chat_channel, chat_message)` expecting a `chat_channel` which was only defined after.
Example exception in logs:
```
Job exception: undefined local variable or method `chat_channel' for Chat::Publisher:Module
/var/www/discourse/plugins/chat/app/services/chat/publisher.rb:91:in `publish_processed!'
/var/www/discourse/plugins/chat/app/jobs/regular/chat/process_message.rb:21:in `block in execute'
/var/www/discourse/lib/distributed_mutex.rb:53:in `block in synchronize'
/var/www/discourse/lib/distributed_mutex.rb:49:in `synchronize'
/var/www/discourse/lib/distributed_mutex.rb:49:in `synchronize'
/var/www/discourse/lib/distributed_mutex.rb:34:in `synchronize'
/var/www/discourse/plugins/chat/app/jobs/regular/chat/process_message.rb:7:in `execute'
/var/www/discourse/app/jobs/base.rb:249:in `block (2 levels) in perform'
```
This commit also:
- adds a spec to ensure oneboxing is not regressing anymore
- increment the version on message processed to ensure callbacks are correctly ran
Note we should also have more tests in `Chat::Publisher`, this will be done when we move it to a proper service.
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