Feature Request: Add mqtt topic as field of recieved message

[claudyus]

I'm using this plugin to indexing and searching mqtt messages. I found that having topic information as message field is a really useful information to have for filtering messages.

Can this be implement?

Thanks

[tduemesnil]

This would help if you listen for a whole tree of Messages like xyz/#

[Warsenius]

@dennisoelkers @bernd is this something that could be added? currently running the input as plaintext. since if i put it in gelf mode the messages are not received at all.

[sirkus7]

I would +1 this request. For most IoT devices, the message only is meaningful if the topic is known.