CVL does not enforce YANG mandatory field validation on OP_CREATE (sonic-mgmt-common #210) #2283

Summary

Cross-posting from sonic-mgmt-common#210 for broader visibility.

CVL's ValidateEditConfig() does not enforce mandatory true YANG fields
on OP_CREATE operations. Entries with missing mandatory fields are silently
accepted and written to CONFIG_DB.

Impact

Affects all sonic YANG models that use mandatory true — not just sonic-acl.

Root Cause (already identified)

Three layers all bypass this validation:

1. YGOT validation is skipped for sonic models (translib/request_binder.go:127)
2. lyd_check_mandatory_tree is commented out in libyang (yparser.go:59)
3. No OP_CREATE mandatory check exists in cvl/cvl_api.go
   (only OP_DELETE has it)

Full details & reproduction steps

--> sonic-net/sonic-mgmt-common#210

Status

A fix has been implemented locally. Waiting for maintainer confirmation
on the intended design before opening a PR in sonic-mgmt-common.