fix(admin): log admin server exceptions and close admin socket

Admin server was crashing silently and requests hang indefinitely.
With this fix, we are now logging the admin server exceptions and also
close the socket afterwards so admin request don't hang.

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>

src/PostgREST/Logger.hs

@@ -160,6 +160,8 @@ observationMessage :: Observation -> Text
 observationMessage = \case
   AdminStartObs address ->
     "Admin server listening on " <> address
+  AdminServerCrashedObs ex ->
+    "FAILURE: Admin server crashed unexpectedly: " <> (showOnSingleLine '\t' . show) ex
   AppStartObs ver ->
     "Starting PostgREST " <> T.decodeUtf8 ver <> "..."
   AppServerAddressObs address ->