feat(examples): add PostgreSQL example with user relationship

Adds an example demonstrating user, comment, and follower relationship
including:
- User management with profiles
- Comments (not really useful, just for showcasing)
- Follower/follozing relationships
- Ineractive CLI interface with CRUD operations
- Database migrations for the example schema

tests/simple_struct.rs

@@ -60,7 +60,10 @@ async fn create_fails_if_already_exists(pool: sqlx::PgPool) -> sqlx::Result<()>
     let result = author.create(&pool).await;
     assert!(result.is_err());
     let error = result.err().unwrap();
-    assert_eq!("error returned from database: duplicate key value violates unique constraint \"authors_pkey\"", error.to_string());
+    assert_eq!(
+        "error returned from database: duplicate key value violates unique constraint \"authors_pkey\"",
+        error.to_string()
+    );
     Ok(())
 }