Skip related endpoints without NATURAL_KEY during awxkit export

[blaipr]

Summary

When exporting resources (e.g. job_templates), the awxkit export code iterates over POST fields from the OPTIONS response. For write_only fields like webhook_key (added to projects in #563, and already present on job templates and workflow job templates), the key appears in both post_fields and _page.related, but the resolved endpoint (e.g. /api/v2/job_templates/N/webhook_key/) is served by a view whose page class (Base) has no NATURAL_KEY defined. This caused the awxkit export to log an ERROR, set _has_error=True, and return None for every affected resource, producing empty asset lists (for example zero job templates in an awxkit collection export).

Fix

When the resolved related endpoint has no NATURAL_KEY attribute, log a warning and skip the field instead of erroring out and dropping the whole resource. A missing NATURAL_KEY means the page class does not participate in natural key resolution at all, which is a different situation from a failed natural key construction, and it should not be fatal.

This fixes the test_export_simple failure in ctrliq/ascender-collection#165, where every JobTemplate was silently dropped from the awxkit export output.

Verification

I ran the ascender-collection unit test suite against this branch (ascender_devel image, pytest tests/unit/): 149 passed, including test_export_simple.

[Copilot]

Pull request overview

This PR fixes awxkit’s asset export flow so that related endpoints which don’t define a NATURAL_KEY (e.g., write-only related endpoints like webhook_key) are skipped instead of causing the entire resource export to fail and drop assets.

Changes:

• Skip related endpoints that lack NATURAL_KEY during _export(), logging a warning instead of erroring out.
• Add webhook_key entries to DEPENDENT_NONEXPORT for Project, JobTemplate, and WorkflowJobTemplate.

[blaipr]

I updated the PR:

• Removed the three DEPENDENT_NONEXPORT entries. That list is only consulted in the related-objects loop, which skips any key already present in post_fields before reaching the check, and webhook_key is a post field. So the entries were never evaluated and the generic NATURAL_KEY skip handles the case on its own.
• Rebased on current main.

Verification: I ran the ascender-collection unit test suite against this branch (ascender_devel image, pytest tests/unit/): 149 passed, including test_export_simple, which fails against main because every JobTemplate gets dropped from the export. This also unblocks ctrliq/ascender-collection#165, whose CI installs awxkit from this repo's default branch, so it would be good to merge this one first.