proxy: remove auth info from http conn info & fixup jwt api trait (#9047)

misc changes split out from #8855 

- **allow cloning the request context in a read-only fashion for
background tasks**
- **propagate endpoint and request context through the jwk cache**
- **only allow password based auth for md5 during testing**
- **remove auth info from conn info**

proxy/src/serverless/conn_pool.rs

@@ -29,11 +29,16 @@ use tracing::{info, info_span, Instrument};
 
 use super::backend::HttpConnError;
 
+#[derive(Debug, Clone)]
+pub(crate) struct ConnInfoWithAuth {
+    pub(crate) conn_info: ConnInfo,
+    pub(crate) auth: AuthData,
+}
+
 #[derive(Debug, Clone)]
 pub(crate) struct ConnInfo {
     pub(crate) user_info: ComputeUserInfo,
     pub(crate) dbname: DbName,
-    pub(crate) auth: AuthData,
 }
 
 #[derive(Debug, Clone)]
@@ -787,7 +792,6 @@ mod tests {
                 options: NeonOptions::default(),
             },
             dbname: "dbname".into(),
-            auth: AuthData::Password("password".as_bytes().into()),
         };
         let ep_pool = Arc::downgrade(
             &pool.get_or_create_endpoint_pool(&conn_info.endpoint_cache_key().unwrap()),
@@ -845,7 +849,6 @@ mod tests {
                 options: NeonOptions::default(),
             },
             dbname: "dbname".into(),
-            auth: AuthData::Password("password".as_bytes().into()),
         };
         let ep_pool = Arc::downgrade(
             &pool.get_or_create_endpoint_pool(&conn_info.endpoint_cache_key().unwrap()),