Start work on storing notifications in the database

crates/collab/src/db/tables/notification.rs

@@ -0,0 +1,29 @@
+use crate::db::{NotificationId, UserId};
+use sea_orm::entity::prelude::*;
+use time::PrimitiveDateTime;
+
+#[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel)]
+#[sea_orm(table_name = "notifications")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub id: NotificationId,
+    pub recipient_id: UserId,
+    pub kind: i32,
+    pub is_read: bool,
+    pub created_at: PrimitiveDateTime,
+    pub entity_id_1: Option<i32>,
+    pub entity_id_2: Option<i32>,
+    pub entity_id_3: Option<i32>,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(
+        belongs_to = "super::user::Entity",
+        from = "Column::RecipientId",
+        to = "super::user::Column::Id"
+    )]
+    Recipient,
+}
+
+impl ActiveModelBehavior for ActiveModel {}