feat(authn-oidc): allow overwriting of cookie name

internal/proxy/director/layer/authn/oidc/authenticator.go

@@ -401,8 +401,14 @@ func (a *Authenticator) getClient(options *LayerOptions, redirectURL string) (*C
 	return client, nil
 }
 
+const defaultCookieNamePrefix = "_bouncer_authn_oidc"
+
 func (a *Authenticator) getCookieName(cookieName string, proxyName store.ProxyName, layerName store.LayerName) string {
-	return strings.ToLower(fmt.Sprintf("%s_%s_%s", cookieName, proxyName, layerName))
+	if cookieName != "" {
+		return cookieName
+	}
+
+	return strings.ToLower(fmt.Sprintf("%s_%s_%s", defaultCookieNamePrefix, proxyName, layerName))
 }
 
 var (