Upload: APIv3 Attachment.create with base64 content (not multipart)

The previous multipart attempt (f74fd07) was rejected by Civi with
"Mandatory key(s) missing: id or content or options.move-file" — the
/civicrm/ajax/rest endpoint on this install doesn't expose $_FILES to
v3 actions; only params['content'] is consulted. Our multipart `file`
part was ignored.

APIv3 Attachment.create has historically been the file-upload entry
point used by Civi's own form widgets and auto-decodes the `content`
field from base64, unlike v4 File.create which stores it verbatim.
Send the same shape we tried first (entity_table, entity_id, name,
mime_type, content=base64) but to v3 Attachment instead of v4 File.

The civi3Upload helper in lib/civicrm.ts is kept in place — it's not
useful for this endpoint but the multipart-POST shape may be needed
later for other Civi entities that do read $_FILES.

app/api/upload/route.ts

@@ -25,7 +25,7 @@
  */
 
 import { NextResponse } from "next/server";
-import { civi3Upload, verifyChecksum } from "@/lib/civicrm";
+import { civi3, verifyChecksum } from "@/lib/civicrm";
 import { allFields } from "@/config/form";
 import { rateLimit, clientIp } from "@/lib/rate-limit";
 
@@ -205,43 +205,39 @@ export async function POST(req: Request) {
     );
   }
 
-  // APIv3 Attachment.create with a multipart `file` part. The earlier
-  // approach used APIv4 File.create with `content: base64String` and that
-  // Civi on this install stores the literal base64 *text* on disk — every
-  // file came back corrupted (hex 6956... = "iVBO..." = base64 PNG header).
-  // APIv3 Attachment.create reads $_FILES['file'] from the multipart body
-  // and writes the bytes through unchanged.
+  // APIv3 Attachment.create with `content` as base64. Path history:
   //
-  // Attachment.create requires (entity_table, entity_id). Our custom-field
-  // flow stores the file id directly in the custom column (no
-  // civicrm_entity_file linkage needed for prefill/download), but the API
-  // still mandates an entity context for the upload call itself, so we
-  // anchor to the form-filler's contact id. The resulting civicrm_entity_file
-  // row is metadata-only — Civi's custom-field joins ignore it.
+  //   1. APIv4 File.create + content:base64 → stored base64 *text* on disk
+  //      (Civi v4 doesn't decode). Every file came back corrupt.
+  //   2. APIv3 Attachment.create + multipart file part → Civi rejected with
+  //      "Mandatory key(s) missing: id or content or options.move-file".
+  //      The /civicrm/ajax/rest endpoint on this install doesn't expose
+  //      $_FILES to the v3 action; only params['content'] is consulted.
+  //   3. APIv3 Attachment.create + content:base64 (this code) → Civi's v3
+  //      Attachment.create has historically been the file-upload entry
+  //      point used by Civi's own form widgets, and it auto-decodes the
+  //      content field.
   //
-  // The returned id is what the frontend stores in RHF state and ultimately
-  // sends as the field value on /api/submit. /api/submit then writes that
-  // id to the activity custom field (stage-N) or to the org contact custom
-  // field (Food_Co_op_Organizing.*).
+  // Attachment.create requires (entity_table, entity_id); our custom-field
+  // flow stores the file id directly in the custom column (no entity_file
+  // linkage needed for prefill/download), but the API still mandates an
+  // entity context, so we anchor to the form-filler's contact id. The
+  // resulting civicrm_entity_file row is metadata-only — Civi's custom-
+  // field joins ignore it.
   //
-  // Orphan files: if the user uploads and then abandons the form, the
-  // civicrm_file + civicrm_entity_file rows persist with no business
-  // reference. Cleanup is handled by a CiviCRM scheduled job (configured
-  // separately by the Civi admin) that prunes orphans older than ~24h.
+  // Orphan files: civicrm_file + civicrm_entity_file rows persist if the
+  // user uploads and then abandons the form. Cleanup is handled by a
+  // CiviCRM scheduled job configured separately by the Civi admin.
   let fileId: number;
   try {
-    const res = await civi3Upload<{ id: string | number }>(
-      "Attachment",
-      "create",
-      {
-        entity_table: "civicrm_contact",
-        entity_id: Number(cid),
-        name: safeName,
-        mime_type: clientMime,
-        sequential: 1,
-      },
-      { bytes, filename: safeName, mime: clientMime },
-    );
+    const res = await civi3<{ id: string | number }>("Attachment", "create", {
+      entity_table: "civicrm_contact",
+      entity_id: Number(cid),
+      name: safeName,
+      mime_type: clientMime,
+      content: Buffer.from(bytes).toString("base64"),
+      sequential: 1,
+    });
     const idRaw = res.values?.[0]?.id;
     const id = typeof idRaw === "string" ? Number(idRaw) : idRaw;
     if (!id || !Number.isFinite(id)) {