Input parameter meta in FileTypeRouter

[bilgeyucel]

Is your feature request related to a problem? Please describe.
When a preprocessing pipeline starts with FileTypeRouter, which is usually the case when we use multiple converters, it's not possible to provide meta information for files

Describe the solution you'd like
Extra meta input parameter that accepts dictionary to add this info to files.
Probably FileTypeRouter will pass this info directly to converters as they route the files

Describe alternatives you've considered

1. Running the converters as a standalone component, adding metadata, running the rest of the preprocessing pipeline
2. Passing the metadata in .run() to converters. This solution is a mess though.

Additional context
Something to think about: Why is the name of the input parameter is "sources" when the component name is FileTypeRouter? Does it make sense to change it to "files"?

[ZanSara]

After a sync with @silvanocerza and @TuanaCelik we agreed to update the converters to accept a single metadata dictionary. In this way, users can use a Multiplexer to provide this dictionary directly to all converters, covering this usecase.

I will also make an example script to explain the solution.

TODO:

• Update text converter: feat: add support for single meta dict in TextFileToDocument #6606
• Update html converter: feat: support single metadata dictionary in HTMLToDocument #6613
• Update azure converter: feat: support single metadata dictionary in AzureOCRDocumentConverter #6635
• Update markdown converter: feat: support single metadata dictionary in MarkdownToDocument #6629
• Update PDF converter: feat: support single metadata dictionary in PyPDFToDocument #6615
• Update Tika converter: feat: support single metadata dictionary in TikaDocumentConverter #6698
• Create Example script: feat: Add example script about routing metadata to converters in indexing pipelines #6702