Start work on storing channel buffers

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

@@ -0,0 +1,37 @@
+use crate::db::BufferId;
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel)]
+#[sea_orm(table_name = "buffer_operations")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub buffer_id: BufferId,
+    #[sea_orm(primary_key)]
+    pub epoch: i32,
+    #[sea_orm(primary_key)]
+    pub lamport_timestamp: i32,
+    #[sea_orm(primary_key)]
+    pub replica_id: i32,
+    pub local_timestamp: i32,
+    pub version: Vec<u8>,
+    pub is_undo: bool,
+    pub value: Vec<u8>,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(
+        belongs_to = "super::buffer::Entity",
+        from = "Column::BufferId",
+        to = "super::buffer::Column::Id"
+    )]
+    Buffer,
+}
+
+impl Related<super::buffer::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Buffer.def()
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}