Add matrix_dendrite_guests_disabled

roles/custom/matrix-dendrite/defaults/main.yml

@@ -240,6 +240,9 @@ matrix_dendrite_client_api_rate_limiting_cooloff_ms: 500
 # Controls whether people with access to the homeserver can register by themselves.
 matrix_dendrite_client_api_registration_disabled: true
 
+# Controls whether guest accounts are disabled
+matrix_dendrite_guests_disabled: true
+
 # reCAPTCHA API for validating registration attempts
 matrix_dendrite_client_api_enable_registration_captcha: false
 matrix_dendrite_client_api_recaptcha_public_key: ""