A simple idea to allow playbooks to control which bit of the role to run

roles/matrix-server/defaults/main.yml

@@ -284,3 +284,12 @@ matrix_ssl_use_staging: false
 
 # Specifies when to attempt to retrieve new SSL certificates from Let's Encrypt.
 matrix_ssl_renew_cron_time_definition: "15 4 */5 * *"
+
+# Variables to Control which parts of the role run.
+run_setup: true
+run_upgrade_postgres: true
+run_start: true
+run_register_user: true
+run_import_sqlite_db: true
+run_import_media_store: true
+run_self_check: true