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: ""

roles/custom/matrix-dendrite/templates/dendrite.yaml.j2

@@ -189,7 +189,7 @@ client_api:
 
   # Prevents new guest accounts from being created. Guest registration is also
   # disabled implicitly by setting 'registration_disabled' above.
-  guests_disabled: true
+  guests_disabled: {{ matrix_dendrite_guests_disabled | to_json }}
 
   # If set, allows registration by anyone who knows the shared secret, regardless of
   # whether registration is otherwise disabled.