[hma] Add notes to hashbank content

[sreeprasad]

Summary

Add the ability to attach notes to hashes when adding content to a bank. Notes provide context about why content was
added (e.g., "Reported by user X on 2024-01-15" or "Part of campaign ABC").

Proposed Changes

Database

• Add a note TEXT field to the BankContent model

API

• Accept optional note parameter when adding content via:
  • POST /bank/<name>/content (file/URL upload)
  • POST /bank/<name>/signal (direct hash)
• Return note in GET /bank/<name>/content/<id> response
• Allow updating note via PUT /bank/<name>/content/<id>

UI

• Add note textarea to the "Add to Bank" modal (all three tabs: File, URL, Hash)
• Display notes when viewing content details
• Allow editing notes on existing content

Tasks

1. DB Schema - Add note column to bank_content table + migration
2. Storage Layer - Update BankContentConfig, bank_add_content(), bank_content_get(), bank_content_update()
3. API Schemas - Add note field to BankedContentMetadata and BankContentResponse
4. API Endpoints - Update curation.py to handle notes
5. Frontend Form - Add textarea to add_to_bank_form.html.j2
6. Frontend JS - Update bank-management.js to send/display notes
7. View/Edit UI - Add UI to view and edit notes on existing content
8. Tests - Add test coverage for notes CRUD

Design Decision

Starting with a single note TEXT field on BankContent. This is simplest approach. All notes will be overwritten with latest note.

Questions for Maintainers

• Should notes have a character limit?
• Should notes be included when exporting/syncing via exchanges?
• Any preference on PR structure (stacked small PRs vs single feature PR)?

[Dcallies]

We talked about this in office hours, and no concerns about adding this - my comment there was to make sure that we added a way to add/view this information as part of the feature.

I am talking to someone about doing #1925, it might be easy to add this as part of this, so mentioned it to them. Let me know @sreeprasad if you are planning on contributing this yourself.

Notes should just be another metadata-like field similar to the content_id / URL. It likely should be limited in length, since folks shouldn't be writing any novels, maybe a sentence or less. This also makes it easier to display inline, and so I'd recommend a length based on that. ~255 characters might be enough (tweet length).

Recommend against including notes as a part of exchange syncing, though in theory it would be possible to map it 1:1 to description in ThreatExchange. This could be added as a followup if we find a pair of users who want to exchange descriptions with each other.

Recommend doing as a stack for ease of review, but if total lines are <500 I'm fine doing it as a big singleton:

1. Add field to database and update internal interfaces to populate/read with unittests
2. Update API to read and write the field as part of bank editing, more unittests
3. Update UI to display notes
4. Update UI to allow writing notes (can combine with previous).

[sreeprasad]

Hello @Dcallies

Yes, i would like to work on this!
I'll start with the DB field and internal interfaces PR and go from there.

[julietshen]

Hi @sreeprasad ! Any update on this one?