fix(accounting): accept delivery contact addresses

[miachillgood]

Description

The live Accounting API can return DELIVERY in Contact.Addresses[].AddressType, while the reusable Address schema only permits POBOX and STREET. Generated SDKs with closed enums therefore fail to deserialize the entire contact.

AddressForOrganisation already includes DELIVERY; this aligns the contact address schema with the observed response and prevents the generated client failure reported in XeroAPI/Xero-NetStandard#666.

The commit uses the repository's Conventional Commits breaking marker because adding a response enum value requires regenerated clients to expose the expanded enum.

Fixes XeroAPI/Xero-NetStandard#666.

Validation

• parsed xero_accounting.yaml successfully
• scripts/api-diff/api-diff.test.sh (9/9 passed)
• API-diff dry run detected the breaking marker and selected allow-breaking mode
• git diff --check

Repository CI will run the official API diff and code-generation validation.

[miachillgood]

I updated the branch onto the latest master and marked the enum expansion with the repository's Conventional Commits breaking marker. The API-diff dry run now selects allow-breaking mode, its 9 conventional-commit tests pass, the YAML parses successfully, and git diff --check passes.

The OpenAPI Spec Diff Check and PR Linting workflows currently show action_required for the external fork. Could a maintainer approve those workflow runs when convenient?