feat: Add FCM analytics label support

[businesscurry123]

Fixes #377

Summary

• Accept analytics_label / analyticsLabel in FCM push data and validate it against Firebase's analytics-label-safe character set and length.
• Forward valid labels into Firebase Admin SDK fcmOptions.analyticsLabel for Android and APNS-over-FCM payloads.
• Keep analytics labels out of user custom payload data and document the new option.

Verification

• npx eslint src/FCM.js spec/FCM.spec.js
• $env:TESTING='1'; npx c8 ./node_modules/.bin/jasmine (167 specs passing)

Summary by CodeRabbit

• New Features

  • Analytics labels are now supported for FCM push notifications on Android and Apple devices with format validation.

• Documentation

  • Added documentation describing analytics label format requirements and example payloads.

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[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds analytics label support to the Parse Server push adapter's FCM implementation. The change enables developers to include an analytics_label field in push requests, which is validated against a regex pattern and then integrated into both APNS and Android FCM payloads under fcmOptions.analyticsLabel.

Changes

FCM Analytics Label Support

Layer / File(s)	Summary
Analytics Label Contract and Validation src/FCM.js	A new analyticsLabelPattern regex validates labels against ^[a-zA-Z0-9-_.~%]{1,50}$. The getAnalyticsLabel() helper extracts analytics_label or analyticsLabel from the request body or data field, validates it, and throws Parse.Error.PUSH_MISCONFIGURED when invalid.
APNS Payload Integration and Tests src/FCM.js, spec/FCM.spec.js	_APNSToFCMPayload() extracts the analytics label and maps it to apns.fcmOptions.analyticsLabel, while excluding analytics label keys from standard payload processing. Tests verify the label is correctly mapped and not included in the APNS payload body.
Android Payload Integration and Tests src/FCM.js, spec/FCM.spec.js	_GCMToFCMPayload() sets android.fcmOptions.analyticsLabel when present and adjusts data handling to copy the data object, remove analytics label and APNS-specific keys before serialization. Tests verify label mapping, exclusion from user data, and validation error handling for invalid labels.
User Documentation README.md	New "Analytics Label" subsection documents the validation pattern, shows how analytics_label in push data is validated and forwarded to Firebase, and includes an example JSON payload.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Suggested reviewers

• dplewis

🚥 Pre-merge checks | ✅ 5 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Engage In Review Feedback	❓ Inconclusive	PR #569 shows single commit with no evidence of review feedback engagement; unclear if PR is awaiting initial review or feedback has been addressed but not committed yet.	Verify whether review feedback was actually given on the PR; if yes, confirm if author engaged in discussion or committed changes addressing feedback.

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description addresses the core requirements with summary, verification, and issue reference, though it lacks the template's structured format with explicit Task checkboxes.
Linked Issues check	✅ Passed	The implementation successfully validates analytics labels against the required regex pattern, forwards valid labels to fcmOptions, and documents the feature as specified in issue #377.
Out of Scope Changes check	✅ Passed	All changes are directly aligned with issue #377 objectives: validation logic, FCM payload integration, and documentation of the analytics label feature.
Security Check	✅ Passed	No security vulnerabilities detected. Regex is safe from ReDoS, input validation is strict, data properly copied and cleaned before use, and no prototype pollution or type confusion risks.
Title check	✅ Passed	The PR title 'feat: add FCM analytics label support' uses the required 'feat:' prefix and clearly summarizes the main change: adding FCM analytics label support functionality.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[parse-github-assistant]

I will reformat the title to use the proper commit message syntax.

[businesscurry123]

Ready for review. I kept the PR focused on FCM analytics label support, added validation coverage, and verified locally with eslint plus the focused Jasmine/c8 suite. The full npm test script is not Windows-shell compatible locally because it uses POSIX env assignment syntax, so I validated the same underlying checks directly.