feat(openfeature): map Source.Fallback.Reason to OpenFeature codes (SDK-130)

[tylerjroach]

Summary

Completes SDK-79 for Java at the OpenFeature layer. Base PR #89 adds `Source.Fallback.Reason` to `SelectedVariant` but the OpenFeature wrapper still uses `result.isFallback()` and collapses every fallback into `ErrorCode.FLAG_NOT_FOUND`. This PR wires the wrapper to the reason.

Branch base

This PR is intentionally branched off `fix/sdk-79-variant-source-fallback-reason` (#89), not `master`, because `Source` doesn't exist on master yet. When #89 merges:

1. This PR's base auto-flips to `master` (GitHub does this when the base branch is deleted)
2. Rebase to drop the base commits and keep only wrapper diff
3. Ready to review on top of merged master

Changes

• `MixpanelProvider.java`:
  • Replace `result.isFallback()` → collapsed `FLAG_NOT_FOUND` with a dispatch on `result.getSource()`. When it's a `Source.Fallback`, call new `mapFallback` helper that switches on the reason.
  • Add `defaultResult` helper for the `NO_ROLLOUT_MATCH` case (spec: DEFAULT reason with no error).
• `pom.xml`:
  • Bump wrapper version `0.1.1` → `0.2.0`
  • Bump base dep `mixpanel-java 1.8.0` → `1.10.0`. 1.10.0 is not yet tagged — release manager may pick a different next-version number; update accordingly.
• `MixpanelProviderTest.java`: 4 new tests, one per `Source.Fallback.Reason` value.

Mapping table

Reason	OpenFeature ErrorCode	Reason
`FLAG_NOT_FOUND`	`FLAG_NOT_FOUND`	`DEFAULT`
`MISSING_CONTEXT_KEY`	`TARGETING_KEY_MISSING`	`ERROR`
`NO_ROLLOUT_MATCH`	(none)	`DEFAULT`
`BACKEND_ERROR`	`GENERAL`	`ERROR`
(unknown)	`GENERAL`	`ERROR`

Matches PHP/Python/Ruby.

Blocked on

• #89 merging to master
• Next mixpanel-java release (`1.10.0` or whatever the release manager picks) containing feat(analytics): add Source discriminated union with Fallback.Reason (SDK-79) #89

Test plan

• Verify existing tests still pass (1-arg SelectedVariant constructor now defaults source to Fallback(FLAG_NOT_FOUND), which the wrapper maps identically)
• Verify 4 new reason-mapping tests pass
• After feat(analytics): add Source discriminated union with Fallback.Reason (SDK-79) #89 merges and next mixpanel-java is released: rebase, update pom.xml version to actual tag, verify CI green

Refs: SDK-130, SDK-79

🤖 Generated with Claude Code

[linear-code]

SDK-79

SDK-130

[greptile-apps]

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
openfeature-provider/src/main/java/com/mixpanel/openfeature/MixpanelProvider.java	Maps each fallback source reason to the corresponding OpenFeature result.
openfeature-provider/src/test/java/com/mixpanel/openfeature/MixpanelProviderTest.java	Adds coverage for all four fallback reason mappings.
openfeature-provider/pom.xml	Updates the mixpanel-java dependency for the new Source API.

_{Reviews (2): Last reviewed commit: "Revert wrapper version bump + drop ratio..." | Re-trigger Greptile}