fix(ui,types): Add Metadata form for collection (#11300)

**What**
- Adds missing Metadata form for collections
- Fixes type of metadata in update payload
- Fixes an issue where deleting the last row of a metadata form would prevent adding new ones.

Resolves SUP-784

packages/admin/dashboard/src/components/forms/metadata-form/metadata-form.tsx

@@ -113,6 +113,15 @@ const InnerForm = <TRes,>({
 
   function deleteRow(index: number) {
     remove(index)
+
+    // If the last row is deleted, add a new blank row
+    if (fields.length === 1) {
+      insert(0, {
+        key: "",
+        value: "",
+        disabled: false,
+      })
+    }
   }
 
   function insertRow(index: number, position: "above" | "below") {