Saves one or more supplier branches as Zuper vendors linked to this provider so you can order from them; send the branches picked from Get Live Supplier Branches. A branch code already saved for this provider is updated in place (name, email, address, job account, favorite flag) instead of duplicated, and branches that can't be created, for example because a vendor with the same name exists, are listed in failed_branches while the request still returns 200. SRS and QXO check each branch_code and preferred_job_account_number with the supplier and return 400 on a mismatch, whereas ABC Supply does not check the branch code but requires both preferred_job_account_number and preferred_job_account_name (a Ship-To account). With update_catalogs_with_linked_products (default true), newly created branches get the catalog of the provider's existing saved branches copied to them, with fresh supplier pricing, in the background. Admin only: the API key must belong to an admin user; other roles receive 405 Access Denied. The provider must exist and be CONNECTED; otherwise the request fails with 404 (unknown provider) or 403 (not connected or reconnect required).