feat: allow domain names or IDs in keystone connector (dexidp#3506)

OpenStack Keystone allows a user to authenticate against a domain. That
domain can be specified either as the domain ID or the domain name when
authenticating. The domain ID is a UUID or the special "default" domain
ID so key off of that when deciding what to submit to the keystone API.
Collapsed the code to share the domainKeystone struct by utilizing
omitempty to skip unset fields.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>

connector/keystone/keystone.go

@@ -10,11 +10,13 @@ import (
 	"log/slog"
 	"net/http"
 
+	"github.com/google/uuid"
+
 	"github.com/dexidp/dex/connector"
 )
 
 type conn struct {
-	Domain        string
+	Domain        domainKeystone
 	Host          string
 	AdminUsername string
 	AdminPassword string
@@ -29,8 +31,8 @@ type userKeystone struct {
 }
 
 type domainKeystone struct {
-	ID   string `json:"id"`
-	Name string `json:"name"`
+	ID   string `json:"id,omitempty"`
+	Name string `json:"name,omitempty"`
 }
 
 // Config holds the configuration parameters for Keystone connector.
@@ -71,13 +73,9 @@ type password struct {
 }
 
 type user struct {
-	Name     string `json:"name"`
-	Domain   domain `json:"domain"`
-	Password string `json:"password"`
-}
-
-type domain struct {
-	ID string `json:"id"`
+	Name     string         `json:"name"`
+	Domain   domainKeystone `json:"domain"`
+	Password string         `json:"password"`
 }
 
 type token struct {
@@ -112,8 +110,22 @@ var (
 
 // Open returns an authentication strategy using Keystone.
 func (c *Config) Open(id string, logger *slog.Logger) (connector.Connector, error) {
+	_, err := uuid.Parse(c.Domain)
+	var domain domainKeystone
+	// check if the supplied domain is a UUID or the special "default" value
+	// which is treated as an ID and not a name
+	if err == nil || c.Domain == "default" {
+		domain = domainKeystone{
+			ID: c.Domain,
+		}
+	} else {
+		domain = domainKeystone{
+			Name: c.Domain,
+		}
+	}
+
 	return &conn{
-		Domain:        c.Domain,
+		Domain:        domain,
 		Host:          c.Host,
 		AdminUsername: c.AdminUsername,
 		AdminPassword: c.AdminPassword,
@@ -202,7 +214,7 @@ func (p *conn) getTokenResponse(ctx context.Context, username, pass string) (res
 				Password: password{
 					User: user{
 						Name:     username,
-						Domain:   domain{ID: p.Domain},
+						Domain:   p.Domain,
 						Password: pass,
 					},
 				},