Add unit tests for main model parts (#310)

Add tests for following models:
- Blog
- Instance
- Media
- User

plume-models/src/post_authors.rs

@@ -1,8 +1,8 @@
-use diesel::{self, QueryDsl, RunQueryDsl, ExpressionMethods};
+use diesel::{self, ExpressionMethods, QueryDsl, RunQueryDsl};
 
 use posts::Post;
-use users::User;
 use schema::post_authors;
+use users::User;
 
 #[derive(Clone, Queryable, Identifiable, Associations)]
 #[belongs_to(Post)]
@@ -10,14 +10,14 @@ use schema::post_authors;
 pub struct PostAuthor {
     pub id: i32,
     pub post_id: i32,
-    pub author_id: i32
+    pub author_id: i32,
 }
 
 #[derive(Insertable)]
 #[table_name = "post_authors"]
 pub struct NewPostAuthor {
     pub post_id: i32,
-    pub author_id: i32
+    pub author_id: i32,
 }
 
 impl PostAuthor {