frontend:chg:generalized form field serialization

frontend/src/routes/auth/about/[id]/+page.server.js

@@ -22,10 +22,15 @@ export const actions = {
    */
   updateUser: async ({ request, fetch, cookies, locals }) => {
     const formData = await request.formData();
-    const firstName = String(formData.get("first_name"));
+    /** @type {Record<string, string>} */
-    const lastName = String(formData.get("last_name"));
+    const updateData = {};
-    const phone = String(formData.get("phone"));
+
-    const birthDate = String(formData.get("birth_date"));
+    // Convert FormData to a plain object
+    formData.forEach((value, key) => {
+      if (typeof value === "string" && value !== "") {
+        updateData[key] = value;
+      }
+    });
 
     const apiURL = `${BASE_API_URI}/backend/users/update/`;
 
@@ -36,12 +41,7 @@ export const actions = {
         "Content-Type": "application/json",
         Cookie: `jwt=${cookies.get("jwt")}`,
       },
-      body: JSON.stringify({
+      body: JSON.stringify(updateData),
-        first_name: firstName,
-        last_name: lastName,
-        phone: phone,
-        birth_date: birthDate,
-      }),
     });
 
     if (!res.ok) {
@@ -57,7 +57,14 @@ export const actions = {
     if (locals.user.date_of_birth) {
       locals.user.date_of_birth = response["date_of_birth"].split("T")[0];
     }
-
+    if (locals.user.membership?.start_date) {
+      locals.user.membership.start_date =
+        locals.user.membership.start_date.split("T")[0];
+    }
+    if (locals.user.membership?.end_date) {
+      locals.user.membership.end_date =
+        locals.user.membership.end_date.split("T")[0];
+    }
     throw redirect(303, `/auth/about/${response.id}`);
   },
   /**