fix: add missing tag.rs

backend/src/entity/tag.rs

@@ -0,0 +1,36 @@
+//! `SeaORM` Entity, @generated by sea-orm-codegen 1.0.0
+
+use super::*;
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
+#[sea_orm(table_name = "tag")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub id: i32,
+    #[sea_orm(unique)]
+    pub name: String,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(has_many = "super::tag_problem::Entity")]
+    TagProblem,
+}
+
+impl Related<tag_problem::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::TagProblem.def()
+    }
+}
+
+impl Related<problem::Entity> for Entity {
+    fn to() -> RelationDef {
+        tag_problem::Relation::Problem.def()
+    }
+    fn via() -> Option<RelationDef> {
+        Some(tag_problem::Relation::Tag.def().rev())
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}