feat(org-settings): add deploy_keys_enabled_for_repositories support

[gdams]

Summary

Adds organization-level control over whether deploy keys may be added to repositories in the org. Maps to the deploy_keys_enabled_for_repositories field on the GitHub Update an organization endpoint.

When set to false, new deploy keys cannot be added on any repository in the organization (existing keys are retained).

Example

settings+: {
  deploy_keys_enabled_for_repositories: false,
},

Changes

• otterdog/models/organization_settings.py — new deploy_keys_enabled_for_repositories: bool field.
• otterdog/resources/schemas/settings.json — schema entry (provider: restapi).
• examples/template/otterdog-defaults.libsonnet — default true on newOrg().
• tests/models/resources/otterdog-org-settings.json + github-org-settings.json + otterdogtest.json — fixture coverage.
• tests/models/test_org_settings.py — assertions and updated to_provider_data length (24 → 25).

Testing

• poetry run pytest tests/ → 243 passed, 2 skipped, 0 failures
• poetry run mypy otterdog → clean
• poetry run ruff check / ruff format --check → clean