feat(router_env): making metric flow as a trait for extensibility (#797)

crates/router/src/routes/metrics/request.rs

@@ -1,6 +1,9 @@
 use super::utils as metric_utils;
 
-pub async fn record_request_time_metric<F, R>(future: F, flow: router_env::Flow) -> R
+pub async fn record_request_time_metric<F, R>(
+    future: F,
+    flow: impl router_env::types::FlowMetric,
+) -> R
 where
     F: futures::Future<Output = R>,
 {

crates/router/src/services/api.rs

@@ -522,7 +522,7 @@ where
     fields(request_method, request_url_path)
 )]
 pub async fn server_wrap<'a, 'b, A, T, U, Q, F, Fut, E>(
-    flow: router_env::Flow,
+    flow: impl router_env::types::FlowMetric,
     state: &'b A,
     request: &'a HttpRequest,
     payload: T,