feat(API): add machine translation settings and locale provider mapping endpoints #STRINGS-2977

[Phrase (phrase-bot)]

This PR was generated by the openapi-apply agent in response to a
/openapi-sync apply request on
Phrase-Engineering/strings-app#18571.

What changed in the API

• GET /api/v2/accounts/{account_id}/machine_translation_settings — new endpoint that returns the account's default MT service, current MTU usage (used/total), and all locale-specific provider overrides.
• PATCH /api/v2/accounts/{account_id}/machine_translation_settings — new endpoint that sets the account's default MT service (default_service).
• POST /api/v2/accounts/{account_id}/machine_translation_locale_provider_mappings — new endpoint that creates a locale-pair-specific provider override (source_locale_code, target_locale_code, service); rejects duplicates for the same locale pair.
• DELETE /api/v2/accounts/{account_id}/machine_translation_locale_provider_mappings — new collection-level delete endpoint that removes a mapping identified by source_locale_code + target_locale_code query parameters (no ID in the path).

Source

• Originating strings-app PR: Phrase-Engineering/strings-app#18571
• Applied by: jablan

---

Opened automatically by the openapi-apply agent. Review the spec changes
against the linked strings-app PR; the agent does not vouch for correctness
beyond "the YAML parsed and the documented layout was followed."

[github-actions]

API changelog (oasdiff)

Doc-only edits (descriptions, examples) do not appear here.

4 changes: 0 error, 0 warning, 4 info
info	[endpoint-added] at doc/compiled.json
	in API DELETE /accounts/{account_id}/machine_translation_locale_provider_mappings
		endpoint added

info	[endpoint-added] at doc/compiled.json
	in API POST /accounts/{account_id}/machine_translation_locale_provider_mappings
		endpoint added

info	[endpoint-added] at doc/compiled.json
	in API GET /accounts/{account_id}/machine_translation_settings
		endpoint added

info	[endpoint-added] at doc/compiled.json
	in API PATCH /accounts/{account_id}/machine_translation_settings
		endpoint added