feat: support meta routing of Answers

[tstadel]

Related Issues

This PR implements supporting anwers with funcitonality already implemented for documents:

• language classification
• metadata routing
• joining

Proposed Changes:

• add common type-check protocol MetaDataclass
• make MetadataRouter work with answers and documents
• add AnswerLanguageClassifier and AnswerJoiner

How did you test it?

• added unittets

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[silvanocerza]

Good idea indeed but I think having a MetaDataclass protocol is a bit overkill, we can just check if an object has the meta field with hasfield(obj, "meta").

It's also quite problematic using the MetaDataclass as output in MetadataRouter, it makes it hard to connect to other components. The output could be either Answer, Document, or ByteStream but a Component that takes Document as input won't accept the connection with MetadataRouter this way.

I'm also wondering whether it makes sense to have different classes to manipulate Answer and Document. Look at the AnswerLanguageClassifier as an example, it's basically identical to DocumentLanguageClassifier apart from the I/O types.

Not saying I'm against it, just wondering whether it's worth duplicating the code. As of now it's not a huge problem since the code is identical apart from the types, but what if we need to differentiate something in the future given the type?

Let's think a bit about this. 🤔

[masci]

Closing as very outdated, feel free to reopen if it's still relevant