Summary
We currently don't record an event when a user submits the Special:CreateAccount form and receives the "Account creation error" page. We should log an event to mediawiki_product_metrics_special_create_account using the same funnel entry token so that we can better understand account creation failures.
Acceptance criteria
- an event is recorded in mediawiki_product_metrics_special_create_account, with the message key used in the error page, and the funnel entry token
