Create blog_authors only when needed

plume-models/src/posts.rs

@@ -706,8 +706,7 @@ impl FromId<DbConn> for Post {
                         cover_id: cover,
                     },
                 )
-            })?;
-
+                .and_then(|post| {
                     for author in authors {
                         PostAuthor::insert(
                             conn,
@@ -718,6 +717,10 @@ impl FromId<DbConn> for Post {
                         )?;
                     }
 
+                    Ok(post)
+                })
+            })?;
+
         // save mentions and tags
         let mut hashtags = md_to_html(&post.source, None, false, None)
             .2