Auth: Do not load users with weird characters in names

If they were registered in earlier versions, you should do something about it:

* Delete them manually.
* Workaround: register a new user to force user storage dump. You can delete them afterwards.

user/files.go

@@ -50,6 +50,9 @@ func usersFromFile() []*User {
 
 func rememberUsers(userList []*User) {
 	for _, user := range userList {
+		if !IsValidUsername(user.Name) {
+			continue
+		}
 		users.Store(user.Name, user)
 	}
 }

user/user.go

@@ -1,7 +1,6 @@
 package user
 
 import (
-	"fmt"
 	"net/http"
 	"strings"
 	"sync"
@@ -136,7 +135,6 @@ func (user *User) ShowLockMaybe(w http.ResponseWriter, rq *http.Request) bool {
 
 // IsValidUsername checks if the given username is valid.
 func IsValidUsername(username string) bool {
-	fmt.Println("Is", username, "ok")
 	for _, r := range username {
 		if strings.ContainsRune("?!:#@><*|\"'&%{}/", r) {
 			return false