post-connection-enable-custom-fieldslisted

# Enable Custom Fields Different customers have different custom fields in their HR/ATS/CRM systems — salary bands, department codes, custom job levels. Rather than hardcoding per-customer fields, a scalable pattern lets customers select which custom fields to enable through a settings UI. ## Prerequisites Custom fields fundamentals loaded (`../implementing-post-connection/references/post-connection-fundamentals.md`). ## Before Proceeding Three pieces of information are needed before generating any code. If invoked from `implementing-post-connection`, the first two were answered in Step 1 — use that context. Otherwise, gather them now: - **Categories**: Which Merge categories need custom fields? (`hris`, `ats`, `crm`, `accounting`, `ticketing`) - **Backend Merge SDK installed?** Search for the language-appropriate package: `@mergeapi/merge-node-client`, `MergePythonClient`, `dev.merge:merge-java-client`, `merge-go-client`, `merge_ruby_client`, or `Merge.Client`. Drives whether examples below use the SDK or raw HTTP. - **Existing field-mapping or settings UI?** If a settings page already exists (see `post-connection-build-settings-page`), the field selector inserts there rather than creating a new page. Then choose the approach (Approach A vs B below) before writing any code — see "Choose Your Approach" immediately after. ## Choose Your Approach Before implementing, ask the user: "There are two approaches for custom fields: - **Approach A (Remote Data)**: No setup r