fix: detect external changes and prevent version_description drift

[austin-engle]

Summary

Fixes drift detection, perpetual plan diff, and version numbering issues with portkey_prompt and portkey_prompt_partial resources.

Problems Fixed

1. External edits invisible to Terraform — Both mapPromptToState and mapPartialToState preserved content from state during Read, ignoring API values. If someone edited a prompt or partial in the Portkey console, Terraform never detected the change.

2. version_description perpetual drift — Both resources imported version_description from the API into state during Read. If set via console but not in Terraform config, this caused an infinite plan loop (state has value → config doesn't → plan nulls it → apply clears it → Read imports it again).

3. MakeDefault targeting wrong version — After creating a new version, the provider called MakeDefault with state.Version + 1, which breaks when versions are created outside Terraform (console edits create gaps in the version sequence).

How It Works

Drift detection: During Read, both mapping functions now compare the API version to the state version:

if API.Version != state.Version → external change → refresh from API

This catches both new versions (console edits) and rollbacks (console sets an older version as default). When versions match, content is preserved from state to avoid false diffs from Portkey API eventual consistency.

Version lookup: After Update creates a new version, the provider calls the /versions list endpoint, matches the returned version UUID against the update response, and gets the real version number for MakeDefault. No more guessing with +1.

version_description: No longer imported from the API — only preserved from state.

Changes

File	Change
client.go	Added ListPromptVersions, ListPromptPartialVersions client methods and response types
prompt_partial_resource.go	Version-comparison drift detection (!=), version lookup via list API, removed version_description API import
prompt_resource.go	Version-comparison drift detection (!=), version lookup via list API, removed version_description API import, parameters refreshed on external change
map_state_test.go (new)	10 unit tests covering drift detection, rollback, state preservation, first population, and version_description behavior

Test Plan

• Unit tests: 10 tests covering all drift detection scenarios
• Manual testing against live Portkey resources in ai-core-dev:
  • Console edit to partial content → detected, Terraform overwrites ✓
  • Console edit to prompt template → detected, Terraform overwrites ✓
  • 5 consecutive console edits (version gap) → apply works, correct version made default ✓
  • Terraform content update → applies correctly, clean plan after ✓
  • No-change plan → clean, no perpetual drift ✓
  • version_description set via console → not imported, no perpetual drift ✓

[roh26it]

Approved

Thoroughly reviewed and tested locally.

What was verified:

• Build, go vet, and gofmt all pass
• All 10 new unit tests pass
• All prompt_partial acceptance tests pass (5/5)
• The 2 failing prompt_resource tests are pre-existing failures on main branch (verified by running the same tests against main)

Code review findings:

• Drift detection logic is sound: Using version comparison (!=) correctly detects both new versions (console edits) and rollbacks
• Version lookup fix is correct: Fetching from /versions endpoint instead of +1 increment handles version gaps caused by out-of-band changes
• version_description fix prevents perpetual drift: No longer importing from API avoids the state/config mismatch cycle
• Tests are meaningful: Verify actual values, not just existence

The changes are well-documented, follow existing patterns, and fix real bugs.