Messages: Allow searching in message headers

[yeikel]

Issue submitter TODO list

• I've searched for an already existing issues here
• I'm running a supported version of the application which is listed here and the feature is not present there

Is your proposal related to a problem?

Currently, the Search within the topic page only searches within the message key and body. There are some use cases where I also need to search in the message header.

Describe the feature you're interested in

Extend the search feature to also include the message headers while searching

Describe alternatives you've considered

No alternative within the UI

Version you're running

c8a8759

Additional context

No response