The instrumentation of blocked account creation attempts was created in T306018. When working on understanding campaign participants being blocked from editing in T366222, the question of whether we can find out if potential campaign participants were blocked from creating an account came up (T366222#10875457).

Based on my reading of the current schema, we cannot answer this because we do not capture anything about the value of the returnTo parameter. If someone comes from a campaign page to create their account, the value of that parameter would reflect that the page is in the Event namespace.

This task proposes to update the instrumentation to also capture the namespace of the associated page if the returnTo parameter is set. Preferably, this would be the numerical namespace id, but the namespace name could be a reasonable alternative if we also know the associated wiki so we can look it up. If the parameter is not set, the instrumentation field should also not be set (i.e. it'll be null).