fix(ipa): correct parent-resource check in resourceBelongsToSingleParent

[DatMitro]

Proposed changes

resourceBelongsToSingleParent normalizes an instance path down to its collection path before checking whether the segment preceding the resource name is a path parameter, but the slice removed two segments instead of one. That left the array still ending in a path parameter and put a plain resource name in the length - 2 slot, so the function returned false for every instance path:

Input (after prefix strip)	Before	After
/groups/{groupId}/clusters/{clusterId}	false	true
/groups/{g}/clusters/{c}/processes/{p}	false	true
/groups/{groupId}	throws TypeError: Cannot read properties of undefined (reading 'startsWith')	false

The throw happened because the slice emptied the array, so resourcePathSections[length - 2] was undefined and isPathParam called .startsWith on it.

Changes:

• Drop one segment with pop() instead of two.
• Simplify the surrounding guards. The two length checks existed only to keep the indexing safe and are subsumed by a single bounds check on the final comparison. Splitting now filters empty segments, matching the idiom already used in isRootLevelResource and longRunningOperations.
• Export the function so it can be unit tested directly, and add cases for nested collections and instances, root-level rejection, non-parameterized parents, prefix-only paths, and consecutive path params.

No change to rule output. The only caller is isSingletonResource, which always passes a resource collection identifier — a path that by definition does not end in a path parameter — so the affected branch was never taken. This is a latent-correctness fix; the full tools/spectral/ipa suite passes unchanged (127 suites, 811 tests).

Jira ticket: CLOUDP-438303

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