Relax SUA validation for malformed bid requests

[sneako]

Summary

• Remove validate_required([:brand]) from BrandVersion — SSPs send SUA with empty or missing brand strings (e.g. "brand": "") which should not invalidate the entire bid request
• Handle "browsers": null in UserAgent changeset — cast_embed(:browsers) raises on null for embeds_many, so we now skip the cast when browsers is not a list
• Add test covering the exact real-world scenario (null browsers + empty platform brand)

Test plan

• All 33 existing tests pass
• New test validates parsing of SUA with "browsers": null and "platform": {"brand": ""}

🤖 Generated with Claude Code

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Note

Low Risk
Small changes to Ecto changesets to tolerate malformed SUA input; low risk but could reduce validation strictness for brand and skip browser casting when the payload is not a list.

Overview
Relaxes V2 structured user-agent handling so malformed client-hint payloads don’t invalidate the whole bid request.

Specifically, BrandVersion no longer requires brand, and UserAgent now only cast_embed(:browsers) when the incoming browsers value is a list (skipping null/non-list values). Adds a regression test that ensures casting succeeds with "browsers": null and an empty platform brand.

^{Written by Cursor Bugbot for commit a2f5d53. This will update automatically on new commits. Configure here.}

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Summary by cubic

Relaxed SUA validation so malformed fields no longer invalidate entire bid requests. Empty/missing platform brand and null browsers are now tolerated.

• Bug Fixes
  • Removed required check for platform brand in BrandVersion; empty or missing brand is accepted.
  • UserAgent safely skips casting browsers unless it’s a list; null input leaves browsers as [].
  • Added a test covering null browsers with an empty platform brand.

^{Written for commit a2f5d53. Summary will update on new commits.}

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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[cubic-dev-ai]

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