proxy: Create disconnect events (#7535)

## Problem

It's not possible to get the duration of the session from proxy events.

## Summary of changes

* Added a separate events folder in s3, to record disconnect events. 
* Disconnect events are exactly the same as normal events, but also have
`disconnect_timestamp` field not empty.
* @oruen suggested to fill it with the same information as the original
events to avoid potentially heavy joins.

proxy/src/serverless/websocket.rs

@@ -156,17 +156,15 @@ pub async fn serve_websocket(
         Err(e) => {
             // todo: log and push to ctx the error kind
             ctx.set_error_kind(e.get_error_kind());
-            ctx.log();
             Err(e.into())
         }
         Ok(None) => {
             ctx.set_success();
-            ctx.log();
             Ok(())
         }
         Ok(Some(p)) => {
             ctx.set_success();
-            ctx.log();
+            ctx.log_connect();
             p.proxy_pass().await
         }
     }