Add ecommerce catalog upload API to Preview spec

[harish-intercom]

Why?

Documents the POST /ecommerce/connectors/{id}/catalog endpoint, which enables integrators to upload product catalogs to an ecommerce connector. The endpoint exists in the API but had no spec coverage.

How?

Adds a new Ecommerce Connectors tag and a POST /ecommerce/connectors/{id}/catalog path in descriptions/0/api.intercom.io.yaml, covering single-file and multipart upload flows via query parameters, with two new response schema components.

Companion PR in developer-docs: https://github.com/intercom/developer-docs/pull/1021

_{Generated with Claude Code}

[zilleeizad-inter]

Reviewed against the actual controller (app/controllers/api/v3/ecommerce/connectors/catalog_controller.rb). Verdict: good to ship to Preview.

Verified accurate against code: the Preview/Unstable version gate (AddEcommerceCatalogUploadApi, registered in the UnstableVersion block), all 8 documented status codes (200/202/400/401/404/409/422/503), all 10 named error codes, the write_content OAuth scope, and the feature-flag 404 message ("The catalog API is not available for this workspace"). Both $refs resolve and fern check is green.

Non-blocking accuracy nits:

1. Missing 422 error code import_job_id_required. The controller returns this (status 422) when finalize is present with part_number != "1" and no import_job_id. Worth adding an example so the multipart error contract is complete — this is the only real gap.
2. finalize enum semantics. Modeling it as a string is correct (not a boolean). But the controller keys on presence + the literal "true", not a validated true/false: any present value enters multipart mode, and only "true" with no file triggers finalize. enum: ['true','false'] slightly over-promises validation. The prose is accurate, so this is low priority.
3. FYI, not changes. intercom_version_invalid (400) is also returned by the version gate but is generic to every Preview endpoint, so omitting it is consistent with the rest of the spec. And path param {id} matches this spec's house style (the focal resource is always {id}) even though the Rails route names it :import_source_id — path params are positional, so it's harmless.

Please keep Intercom-OpenAPI#580 and developer-docs#1021 identical — any of the above should be applied to both.

Companion PRs: #580 ↔ intercom/developer-docs#1021

~ Automated via Claude

[zilleeizad-inter]

Approving. ✅ Good for Preview.

Re-verified after the latest push: the new 422 import_job_id_required example matches the controller verbatim (code + message + status), the endpoint is correctly gated to the Preview/Unstable version, and all status/error codes, the write_content scope, and the feature-flag 404 line up with app/controllers/api/v3/ecommerce/connectors/catalog_controller.rb. fern check is green, and this PR is byte-identical to its companion.

Merge order reminder: land developer-docs#1021 first, then Intercom-OpenAPI#580.

~ Automated via Claude