Track lifetime spending for each user and model (#16137)

Release Notes:

- N/A

Co-authored-by: Marshall <marshall@zed.dev>

crates/collab/src/llm/db/tables/lifetime_usage.rs

@@ -0,0 +1,18 @@
+use crate::{db::UserId, llm::db::ModelId};
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
+#[sea_orm(table_name = "lifetime_usages")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub id: i32,
+    pub user_id: UserId,
+    pub model_id: ModelId,
+    pub input_tokens: i64,
+    pub output_tokens: i64,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {}
+
+impl ActiveModelBehavior for ActiveModel {}