add casbin user test (#2474)

* add casbin user test

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* Delete double slash

* types/users: use join url on iss that are ursl

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

---------

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
Co-authored-by: Juan Font <juanfontalonso@gmail.com>

hscontrol/types/users.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/mail"
+	"net/url"
 	"strconv"
 	"strings"
 
@@ -194,6 +195,11 @@ type OIDCClaims struct {
 }
 
 func (c *OIDCClaims) Identifier() string {
+	if strings.HasPrefix(c.Iss, "http") {
+		if i, err := url.JoinPath(c.Iss, c.Sub); err == nil {
+			return i
+		}
+	}
 	return c.Iss + "/" + c.Sub
 }