Decouple emailservice from app package (#17827)

* decouple emailservice from app package

* fix some escaped errors

* move email package under app directory

* fix i18n

* reflect review comments

app/web_hub_test.go

@@ -168,6 +168,7 @@ func TestHubSessionRevokeRace(t *testing.T) {
 		ConfigFn:     th.App.srv.Config,
 		Metrics:      th.App.Metrics(),
 		Cluster:      th.App.Cluster(),
+		LicenseFn:    th.App.srv.License,
 	})
 	require.NoError(t, err)
 	th.App.srv.userService = userService