fix: resolve P1 backend consistency issues

server/user.go

@@ -3,6 +3,7 @@ package main
 import (
 	"container/heap"
 	crand "crypto/rand"
+	"errors"
 	"math/rand"
 	"strings"
 	"time"
@@ -216,7 +217,11 @@ func replyCreateUser(s *Session, msg *ClientComMessage, rec *auth.Rec) {
 	// Create user record in the database.
 	if _, err := store.Users.Create(s.tenantID, &user, private); err != nil {
 		logs.Warn.Println("create user: failed to create user", err, "sid=", s.sid)
-		s.queueOut(ErrUnknown(msg.Id, "", msg.Timestamp))
+		params := map[string]any(nil)
+		if errors.Is(err, types.ErrDuplicate) && phoneRegistration {
+			params = map[string]any{"what": "phone", "reason": "PHONE_ALREADY_REGISTERED"}
+		}
+		s.queueOut(decodeStoreError(err, msg.Id, msg.Timestamp, params))
 		return
 	}