Langfuse tags and user_id on Haystack

Is your feature request related to a problem? Please describe.
We’ve started using Haystack to create LLM pipelines and want to track their usage with Langfuse. We use a function that returns a Haystack pipeline with the LLM and Langfuse tracer.

Currently, we rely heavily on tags in Langfuse (as we do with LangChain) to monitor usage across teams, projects, and other contexts, but there doesn’t seem to be a way to implement this functionality in Haystack. Additionally, assigning a user to a trace is a key feature we use, and we haven’t found a way to do this in Haystack either. This lack of integration limits our ability to track and manage usage effectively.

Describe the solution you’d like
We’d like the ability to use langfuse tags and user_id associated to a trace in Haystack pipelines to track usage for various teams and projects. Seamless integration of these features would improve our workflow significantly.

Describe alternatives you’ve considered
We’ve looked into potential workarounds, such as using the trace URL after getting the response and setting up this parameters, but this approach is cumbersome and would require to change the way we usually work with LLMs.