collab: Remove GET /billing/monthly_spend endpoint (#31123)

This PR removes the `GET /billing/monthly_spend` endpoint, as it is no
longer used.

Release Notes:

- N/A

crates/collab/src/llm/db/queries/usages.rs

@@ -1,7 +1,3 @@
-use crate::db::UserId;
-use crate::llm::Cents;
-use chrono::Datelike;
-use futures::StreamExt as _;
 use std::str::FromStr;
 use strum::IntoEnumIterator as _;
 
@@ -45,68 +41,4 @@ impl LlmDatabase {
             .collect();
         Ok(())
     }
-
-    pub async fn get_user_spending_for_month(
-        &self,
-        user_id: UserId,
-        now: DateTimeUtc,
-    ) -> Result<Cents> {
-        self.transaction(|tx| async move {
-            let month = now.date_naive().month() as i32;
-            let year = now.date_naive().year();
-
-            let mut monthly_usages = monthly_usage::Entity::find()
-                .filter(
-                    monthly_usage::Column::UserId
-                        .eq(user_id)
-                        .and(monthly_usage::Column::Month.eq(month))
-                        .and(monthly_usage::Column::Year.eq(year)),
-                )
-                .stream(&*tx)
-                .await?;
-            let mut monthly_spending = Cents::ZERO;
-
-            while let Some(usage) = monthly_usages.next().await {
-                let usage = usage?;
-                let Ok(model) = self.model_by_id(usage.model_id) else {
-                    continue;
-                };
-
-                monthly_spending += calculate_spending(
-                    model,
-                    usage.input_tokens as usize,
-                    usage.cache_creation_input_tokens as usize,
-                    usage.cache_read_input_tokens as usize,
-                    usage.output_tokens as usize,
-                );
-            }
-
-            Ok(monthly_spending)
-        })
-        .await
-    }
-}
-
-fn calculate_spending(
-    model: &model::Model,
-    input_tokens_this_month: usize,
-    cache_creation_input_tokens_this_month: usize,
-    cache_read_input_tokens_this_month: usize,
-    output_tokens_this_month: usize,
-) -> Cents {
-    let input_token_cost =
-        input_tokens_this_month * model.price_per_million_input_tokens as usize / 1_000_000;
-    let cache_creation_input_token_cost = cache_creation_input_tokens_this_month
-        * model.price_per_million_cache_creation_input_tokens as usize
-        / 1_000_000;
-    let cache_read_input_token_cost = cache_read_input_tokens_this_month
-        * model.price_per_million_cache_read_input_tokens as usize
-        / 1_000_000;
-    let output_token_cost =
-        output_tokens_this_month * model.price_per_million_output_tokens as usize / 1_000_000;
-    let spending = input_token_cost
-        + cache_creation_input_token_cost
-        + cache_read_input_token_cost
-        + output_token_cost;
-    Cents::new(spending as u32)
 }

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

@@ -1,5 +1,4 @@
 pub mod model;
-pub mod monthly_usage;
 pub mod provider;
 pub mod subscription_usage;
 pub mod subscription_usage_meter;

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

@@ -1,22 +0,0 @@
-use crate::{db::UserId, llm::db::ModelId};
-use sea_orm::entity::prelude::*;
-
-#[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
-#[sea_orm(table_name = "monthly_usages")]
-pub struct Model {
-    #[sea_orm(primary_key)]
-    pub id: i32,
-    pub user_id: UserId,
-    pub model_id: ModelId,
-    pub month: i32,
-    pub year: i32,
-    pub input_tokens: i64,
-    pub cache_creation_input_tokens: i64,
-    pub cache_read_input_tokens: i64,
-    pub output_tokens: i64,
-}
-
-#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
-pub enum Relation {}
-
-impl ActiveModelBehavior for ActiveModel {}