accounts: reduce initial load time even further

took the referralCache idea further and did it for all db queries. Now
take ~40ms for ~5000 users on arm64 through QEMU, and ~60ms on a
rockpro64.

users.go

@@ -141,7 +141,7 @@ func (app *appContext) NewUserPostVerification(p NewUserParams) (out NewUserData
 
 	webhookURIs := app.config.Section("webhooks").Key("created").StringsWithShadows("|")
 	if len(webhookURIs) != 0 {
-		summary := app.userSummary(out.User, nil)
+		summary := app.GetUserSummary(out.User)
 		for _, uri := range webhookURIs {
 			pendingTasks.Add(1)
 			go func() {