Fix opslevel_service dropping preferred_api_document_source when api_document_path is unset (#14748)

[saditya370]

Summary

Fixes #14748. Configuring preferred_api_document_source on opslevel_service without also setting api_document_path caused apply to fail with Provider produced inconsistent result after apply: .preferred_api_document_source: was cty.StringVal("PUSH"), but now null. The provider was gating the serviceApiDocSettingsUpdate mutation behind a non-empty api_document_path, so the user's preferred-source value was never sent to the backend — Terraform's plan/state consistency check then rejected the apply.

This is a provider-only fix. The GraphQL backend and opslevel-go client already accepted the two arguments independently; only the provider was incorrectly coupling them.

Changes

• Add serviceApiDocSettingsUpdateInput(plan, state) helper in opslevel/resource_opslevel_service.go that decides when to call ServiceApiDocSettingsUpdate and with what arguments. Returns shouldUpdate=true whenever either field is configured in plan, or whenever either field was previously managed in state (so unsetting still works).
• Create now uses the helper, fixing source-only configs.
• Update now uses the same helper, fixing the prior bug where api_document_path being null silently cleared preferred_api_document_source.
• Behavior is unchanged for path-only and path-plus-source configs — the helper returns the same arguments the old code sent.

Customer-reported repro

resource "opslevel_service" "example" {
  name                          = "example"
  preferred_api_document_source = "PUSH"
}

Before the fix: terraform apply errored with the inconsistent-result message and left an orphaned service in OpsLevel that Terraform did not record in state.

After the fix: apply succeeds, and a follow-up terraform plan reports No changes.

Test plan

• New unit tests for serviceApiDocSettingsUpdateInput covering source-only PUSH, source-only PULL, path-only, unmanaged, unset previously-managed source, and unset previously-managed path — see opslevel/resource_opslevel_service_test.go.
• New tftest regression resource_service_create_with_preferred_api_document_source_without_path reproducing the exact customer config and asserting api_document_path == null and preferred_api_document_source == "PUSH" after apply — see tests/service.tftest.hcl.
• GOWORK=off go test ./opslevel passes.
• GOWORK=off go vet ./... clean.
• GOWORK=off task test passes (104 Terraform tests + Go unit tests).
• Verified end-to-end against a live OpsLevel tenant: source-only PUSH and PULL configs apply cleanly, idempotent on re-plan, and the resulting services row in the database has the expected api_docs_source value with api_docs_path null.

[andrewstillv15]

This helper should live at the bottom of the file since it isn't global.

[andrewstillv15]

The naming for these variables doesn't make much sense as these attributes are always managed.

[andrewstillv15]

We can remove the state argument if we put the plan/state equality check into the update lifecycle method.

[saditya370]

Refactored as suggested

1. helper moved to bottom of file,
2. dropped the state arg,
3. equality check moved into Update.