feat: create a model for subtasks

src/schema/mod.rs

@@ -9,6 +9,17 @@ diesel::table! {
     }
 }
 
+diesel::table! {
+    subtasks (id) {
+        id -> Int4,
+        task_id -> Int4,
+        title -> Text,
+        is_completed -> Bool,
+        created_at -> Timestamp,
+        updated_at -> Timestamp,
+    }
+}
+
 diesel::table! {
     tasks (id) {
         id -> Int4,
@@ -21,9 +32,11 @@ diesel::table! {
     }
 }
 
+diesel::joinable!(subtasks -> tasks (task_id));
 diesel::joinable!(tasks -> projects (project_id));
 
 diesel::allow_tables_to_appear_in_same_query!(
     projects,
+    subtasks,
     tasks,
 );