fix(js/plugin/compat-oai): preserve legacy image URL handling when contentType is missing

[7hokerz]

Description here... Help the reviewer by:

• Keeps existing behavior for media without explicit contentType
• Applies strict validation only when contentType is explicitly provided
• Prevents breaking existing integrations relying on signed URLs
• Fixed this issue: [JS] Image URLs via {{media url=image}} fail after update — is this intended? #4196

Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually, unit tested, etc.)
• Docs updated (updated docs or a docs bug required)

[gemini-code-assist]

Summary of Changes

Hello @7hokerz, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where media parts lacking an explicit content type were not being handled as expected, particularly impacting integrations using signed URLs. The changes ensure backward compatibility by defaulting to an image_url interpretation for such media, thereby preventing disruptions to existing systems.

Highlights

• Legacy Image URL Handling: Introduced logic to preserve legacy behavior for media parts without an explicit contentType, treating them as image_url types. This ensures that existing integrations relying on signed URLs or remote images without metadata continue to function correctly.
• Strict Validation: The strict validation for media types is now applied only when a contentType is explicitly provided, preventing unintended breakage for media where this information might be missing.
• New Test Case: Added a new test case to verify that signed URLs are correctly transformed into image_url types when no contentType is specified.

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[gemini-code-assist]

Code Review

This pull request correctly preserves legacy behavior for media without an explicit contentType by treating them as image URLs, which is a good addition for backward compatibility. The change is well-tested with a new unit test for signed URLs. My review includes one suggestion for refactoring in js/plugins/compat-oai/src/model.ts to reduce code duplication and improve maintainability by combining two conditional blocks with similar logic.

[xavidop]

LGTM

[7hokerz]

LGTM

@xavidop Thanks a lot for the review! should I just wait for a maintainer's final check?

[xavidop]

LGTM

@xavidop Thanks a lot for the review! should I just wait for a maintainer's final check?

yes, @pavelgj can you have a look?