feat: add custom metadata support for document tasks

[kumarUjjawal]

Pull Request

Related issue

Fixes #733

What does this PR do?

• ...

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Summary by CodeRabbit

• New Features
  • Added custom metadata support for all document operations. Users can now attach optional custom metadata to add, update, and delete operations. Metadata is preserved and included in task responses, enabling better tracking, categorization, and monitoring of document operations throughout their lifecycle.

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