added OAuth2 displayName and pkce options

tools/auth/twitch.go

@@ -24,11 +24,13 @@ type Twitch struct {
 // NewTwitchProvider creates new Twitch provider instance with some defaults.
 func NewTwitchProvider() *Twitch {
 	return &Twitch{&baseProvider{
-		ctx:        context.Background(),
-		scopes:     []string{"user:read:email"},
-		authUrl:    twitch.Endpoint.AuthURL,
-		tokenUrl:   twitch.Endpoint.TokenURL,
-		userApiUrl: "https://api.twitch.tv/helix/users",
+		ctx:         context.Background(),
+		displayName: "Twitch",
+		pkce:        true,
+		scopes:      []string{"user:read:email"},
+		authUrl:     twitch.Endpoint.AuthURL,
+		tokenUrl:    twitch.Endpoint.TokenURL,
+		userApiUrl:  "https://api.twitch.tv/helix/users",
 	}}
 }