feat: Set ByteStream's mime_type attribute for web based resources

[vblagoje]

Why:

Enhances consistency and clarity in handling MIME types in ByteStream across Haystack. ByteStream's mime_type attribute gets set properly for web originating ByteStreams. In web originating ByteStream's content_type is still left intact in meta dictionary for backward compatibility.

• fixes FileTypeRouter should get mime type from ByteStream mime type attribute instead of `meta #7633

What:

• Sets mime_type attribute of ByteStream instead of indirect storage of MIME types within a meta dictionary. This change allows direct and uniform access to MIME types, simplifying handling for both web resources and local files.

How can it be used:

• Fetching and Routing Based on MIME Types: Users can now straightforwardly fetch and route documents based on their MIME types, applying specific processing or handling routines directly:

  if stream.mime_type == "application/pdf":
      # Process PDF stream

• Enhanced Clarity in Code: The management of MIME types is simplified, enhancing code readability and reducing potential for errors by avoiding nested data structures.

How did you test it:

• Unit tests in test_file_router.py were adjusted to reflect the direct assignment and checking of mime_type.
• Tests confirm correct assignment, access, and utilization of the mime_type attribute across components, ensuring accurate management and application for routing and processing.
• Integration testing may be conducted to verify consistent utilization across processing pathways and to confirm no impact on existing functionalities.

Notes for the reviewer:

• Please ensure the mime_type attribute implementation covers all necessary cases where MIME type information is accessed or modified.
• Special attention might be required to ensure backward compatibility or migration from the previous approach using the meta dictionary.

[coveralls]

Pull Request Test Coverage Report for Build 9058615189

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 5 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.01%) to 90.402%

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Files with Coverage Reduction	New Missed Lines	%
components/fetchers/link_content.py	5	78.31%

Totals
Change from base Build 9030307905:	-0.01%
Covered Lines:	6527
Relevant Lines:	7220

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💛 - Coveralls

[vblagoje]

@shadeMe @wochinge has all the context already and understands the nuances of the changes compared to the previous one we dropped. Assigning this review to him 🙏

[wochinge]

Nice, clean solution! 💯