Add gallery item deletion + making them optional (#224)

src/database/models/project_item.rs

@@ -370,6 +370,16 @@ impl Project {
         .execute(&mut *transaction)
         .await?;
 
+        sqlx::query!(
+            "
+            DELETE FROM mods_gallery
+            WHERE mod_id = $1
+            ",
+            id as ProjectId
+        )
+        .execute(&mut *transaction)
+        .await?;
+
         sqlx::query!(
             "
             DELETE FROM mod_follows