Make gallery item featuring exclusive (#241)

* Make gallery featured value exclusive

* Run prepare

src/routes/project_creation.rs

@@ -442,6 +442,12 @@ pub async fn project_create_inner(
         }
 
         if let Some(gallery_items) = &project_create_data.gallery_items {
+            if gallery_items.iter().filter(|a| a.featured).count() > 1 {
+                return Err(CreateError::InvalidInput(String::from(
+                    "Only one gallery image can be featured.",
+                )));
+            }
+
             if let Some(item) = gallery_items.iter().find(|x| x.item == name) {
                 let mut data = Vec::new();
                 while let Some(chunk) = field.next().await {