feat(backlog): save only the changed fields

src/utils/backlog.js

@@ -14,15 +14,24 @@ export const toBacklogRequest = ({status, rating, notes, priority}) => ({
 });
 
 /**
- * PUT /api/library/games/{appid}/backlog. The caller handles the response status.
- *
- * @param entry a backlog entry in request form, see toBacklogRequest
+ * The fields of `form` that differ from `saved`, in request form: what saveBacklogEntry sends.
  */
-export const saveBacklogEntry = (appid, entry) =>
+export const changedFields = (saved, form) => {
+    const before = toBacklogRequest(saved);
+    return Object.fromEntries(Object.entries(toBacklogRequest(form)).filter(([field, value]) => value !== before[field]));
+};
+
+/**
+ * PATCH /api/library/games/{appid}/backlog with only the changed fields, so an older tab keeps the newer ones; null
+ * clears a field. Answers the whole entry. The caller handles the response status.
+ *
+ * @param changes see changedFields
+ */
+export const saveBacklogEntry = (appid, changes) =>
     apiFetch(`${import.meta.env.VITE_CORE_API_URL}/api/library/games/${appid}/backlog`, {
-        method: 'PUT',
+        method: 'PATCH',
         headers: {'Content-Type': 'application/json'},
-        body: JSON.stringify(entry),
+        body: JSON.stringify(changes),
     });
 
 /**