multipart middleware (#5809)

* fix: multipart middleware

* fix: reviews

server/middlewares/multipart.ts

@@ -0,0 +1,37 @@
+import { Next } from "koa";
+import { bytesToHumanReadable } from "@shared/utils/files";
+import { InvalidRequestError } from "@server/errors";
+import { APIContext } from "@server/types";
+import { getFileFromRequest } from "@server/utils/koa";
+
+export default function multipart({
+  maximumFileSize,
+}: {
+  maximumFileSize: number;
+}) {
+  return async function multipartMiddleware(ctx: APIContext, next: Next) {
+    if (!ctx.is("multipart/form-data")) {
+      ctx.throw(
+        InvalidRequestError("Request type must be multipart/form-data")
+      );
+    }
+
+    const file = getFileFromRequest(ctx.request);
+    if (!file) {
+      ctx.throw(InvalidRequestError("Request must include a file parameter"));
+    }
+
+    if (file.size > maximumFileSize) {
+      ctx.throw(
+        InvalidRequestError(
+          `The selected file was larger than the ${bytesToHumanReadable(
+            maximumFileSize
+          )} maximum size`
+        )
+      );
+    }
+
+    ctx.input = { ...(ctx.input ?? {}), file };
+    return next();
+  };
+}