ci: add workflow to regenerate models from OpenAPI spec changes

[vdusek]

Summary

• Add a workflow_dispatch workflow (regenerate_models.yaml) that is triggered from apify-docs when OpenAPI specification changes in a PR
• The workflow checks out apify-docs at the PR branch, builds the bundled OpenAPI spec, regenerates Pydantic models via datamodel-codegen, and opens a PR if models changed
• Includes concurrency control (re-triggers for the same docs PR cancel previous runs)
• Comments on the source apify-docs PR via the service account

How it works

PR in apify-docs (changes openapi specs)
  → openapi-ci.yaml: lint → build → validate → trigger-client-model-regeneration
    → gh workflow run regenerate_models.yaml in apify-client-python
      → Build spec from PR branch → datamodel-codegen → PR + comment on docs PR

Prerequisites

• APIFY_SERVICE_ACCOUNT_GITHUB_TOKEN secret must exist in this repo
• NPM_TOKEN secret for building apify-docs dependencies
• This workflow must be merged to master before the corresponding trigger is added to apify-docs

Related

• apify-docs counterpart: apify/apify-docs (adds trigger job to openapi-ci.yaml)

Test plan

• Merge this PR first
• Then merge the apify-docs counterpart
• Create a test PR in apify-docs that changes files in apify-api/openapi/
• Verify the workflow is triggered and creates a PR in this repo

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.57%. Comparing base (3fee70a) to head (971f9d0).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #657      +/-   ##
==========================================
+ Coverage   96.52%   96.57%   +0.04%     
==========================================
  Files          45       45              
  Lines        4318     4318              
==========================================
+ Hits         4168     4170       +2     
+ Misses        150      148       -2     

Flag	Coverage Δ
integration	94.69% <ø> (+0.13%)	⬆️
unit	78.04% <ø> (ø)

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