Start work on storing channel buffers

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

@@ -0,0 +1,32 @@
+use crate::db::BufferId;
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel)]
+#[sea_orm(table_name = "buffers")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub id: BufferId,
+    pub epoch: i32,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(has_many = "super::buffer_operation::Entity")]
+    Operations,
+    #[sea_orm(has_many = "super::buffer_snapshot::Entity")]
+    Snapshots,
+}
+
+impl Related<super::buffer_operation::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Operations.def()
+    }
+}
+
+impl Related<super::buffer_snapshot::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Snapshots.def()
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}