Describe the bug
Looking at this code here:

The ByteStream class has an attribute mime_type. We should rather using this than using the metadata for this.

Error message
None

Expected behavior
Use mime_type field instead of meta (or make this configurable)

Additional context
Add any other context about the problem here, like document types / preprocessing steps / settings of reader etc.

To Reproduce
Steps to reproduce the behavior

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System:

• OS:
• GPU/CPU:
• Haystack version (commit or version number): 2
• DocumentStore:
• Reader:
• Retriever: