feat(ipa): Add IPA-111 validation rules

[mongodb-sage-bot]

Proposed changes

Add three new Spectral validation rules enforcing lintable IPA-111 (Default Values) constraints to the IPA Validation Framework:

• xgen-IPA-111-optional-fields-no-default: optional (non-required) fields must not define a default value. Boolean fields are delegated to the boolean rule below, and fields marked with the new x-xgen-server-computed-when-client-omitted extension are exempt.
• xgen-IPA-111-effective-fields-read-only: effective-value fields (property names prefixed with effective) must be readOnly: true and must not appear in request schemas.
• xgen-IPA-111-optional-boolean-fields-default-false: optional boolean fields must default to false.

Also adds the IPA-111.yaml ruleset, registers it in ipa-spectral.yaml, regenerates the ruleset README, and introduces shared helpers isRequiredProperty (schemaUtils) and hasServerComputedWhenClientOmittedExtension (extensions).

Jira ticket: CLOUDP-439595

Checklist

• I have signed the MongoDB CLA
• I have added tests that prove my fix is effective or that my feature works

Changes to Spectral

• I have read the README file for Spectral Updates

---

Important

MongoDB Contribution Guidelines

This pull request was generated by sage-bot on behalf of yeliz.henden@mongodb.com (ticket assignee). The assignee must self-review the changes before requesting review from another engineer.
The assignee is not allowed to merge their own PR without approval from another engineer.

• yeliz.henden@mongodb.com has read and agrees to the MongoDB AI Policy
• yeliz.henden@mongodb.com has self-reviewed this PR before requesting review from another engineer

[mongodb-sage-bot]

Sage Bot can help with this pull request. Just @sage-bot in comments and I'll start working on changes in this branch.
_{Learn more about Sage Bot}

[mongodb-sage-bot]

❌ Sage Bot - Unexpected Error

Sage Bot ran into an unexpected error processing your request. If you need help, reach out in #ask-devprod.

[wtrocki]

The 3 new rules are correctly implemented and all tests pass. The issue is the override list only covered ~64 of 318 actual violations in the Atlas v2 spec — running ipa-validation against v2.yaml would fail with 254 errors.
I expanded the override list to cover all 318 violations:

• xgen-IPA-111-optional-boolean-fields-default-false: 44 → 209 entries
• xgen-IPA-111-optional-fields-no-default: 19 → 96 entries
• xgen-IPA-111-effective-fields-read-only: 1 → 13 entries

Concern — sheer volume of exceptions: 318 overrides for a single IPA rule is a red flag. The majority are boolean fields in response-only schemas (e.g., BackupSnapshot, DiskBackupSnapshotRestoreJob, ClusterDescriptionProcessArgs) where default: false is semantically irrelevant — the server computes these values.

@yelizhenden-mdb Once we you back we should align and consider:

1. Scoping optional-boolean-fields-default-false to request schemas only — responses don't benefit from default annotations
2. Similarly for optional-fields-no-default — response defaults serve as API documentation
3. Whether the effective-fields rule should only fire in request contexts (already partially done via pathIsForRequestVersion)
   If scoped to requests only, the override list would shrink from 318 to ~50 entries (rough estimate). Worth a follow-up before CLOUDP-439952 gets too large.

I'm going to do provisional change for this so it is easier to make follow up IPA change.