Release 4.15.4 with Singular integration attribute

[anglinb]

Summary

• Bumps SuperwallKit to 4.15.4 from the current master release base
• Adds singularDeviceId to IntegrationAttribute
• Covers serialization in attribution tests
• Adds the 4.15.4 changelog entry

Release behavior

Merging this into master should trigger .github/workflows/tag-version.yml, which tags 4.15.4, creates release/4.15.4, and publishes CocoaPods.

Verification

• git diff --check

Local builds/tests not run; branch push will run the repo GitHub Actions.

[greptile-apps]

PR author is not in the allowed authors list.

[pullfrog]

✅ No new issues found.

Reviewed changes — release cut for SuperwallKit 4.15.4 adding the Singular device identifier as a new integration attribute.

• Add singularDeviceId to IntegrationAttribute — new enum case appended last in IntegrationAttribute.swift, preserving the Int raw values of every existing case (no serialization-ordering breakage), with the matching "singularDeviceId" mapping in the CustomStringConvertible.description switch.
• Version bump to 4.15.4 — synchronized across all three required files: Constants.swift (sdkVersion), SuperwallKit.podspec (s.version), and a new top CHANGELOG.md entry under ### Enhancements.
• Test coverage — AttributionTests.swift adds .singularDeviceId to the input dictionary and asserts the stored prop round-trips as "singular-device-id".

The description switch is the only exhaustive switch over the enum and handles the new case; all other usage is keyed by string (AttributionFetcher merge logic), so no other call site needs updating. Version strings are consistent across all three files, and the changelog entry is correctly placed above 4.15.3. Base is master, matching the release workflow trigger.

  ^{｜ View workflow run ｜ Using Claude Opus ｜ 𝕏}