Add buffer integration test

Rearrange channel crate structure
Get channel buffer from database

co-authored-by: Max <max@zed.dev>

crates/client/src/client.rs

@@ -1,10 +1,6 @@
 #[cfg(any(test, feature = "test-support"))]
 pub mod test;
 
-#[cfg(test)]
-mod channel_store_tests;
-
-pub mod channel_store;
 pub mod telemetry;
 pub mod user;
 
@@ -48,7 +44,6 @@ use util::channel::ReleaseChannel;
 use util::http::HttpClient;
 use util::{ResultExt, TryFutureExt};
 
-pub use channel_store::*;
 pub use rpc::*;
 pub use telemetry::ClickhouseEvent;
 pub use user::*;