Store the context source file or URL when using document loader
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## Summary
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Follow-up to:
- #3569310+s
- #3586275+s
We can load context content from files and URLs now. We still would like to track the source document for reference.
## Problem
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What is currently difficult, missing, or frustrating?
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We don't track the source document when loading context content via document loader (mdxeditor load document button).
## Proposed solution *(optional)*
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Document loader doesn't currently have a way of grabbing this information. A new hook would be needed. Then we'd use that to store this information for reference.
## Workaround *(optional)*
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For files, the user actually uploads the file, so the file is in the system unless they delete it. For URLs, that's not the case though.
## Affected functional areas *(optional)*
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List the areas or sub-modules of the AI Context module this request relates to.
Examples: context items, scope plugins, context selection, subcontext, admin UI
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- Context items
- ai_context_document_loader submodule
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