===Acceptance criteria===
Given that I am allowed to organize events:
When I create an event using Special:EnableEventRegistration
AND there is a single permitted namespace for event registration
Then the event page field will autocomplete page titles for that namespace only.
When I create an event using Special:EnableEventRegistration
AND there are more than one permitted namespace for event registration
Then the event page field will autocomplete page titles for all namespaces, not just the allowed ones (this limitation is addressed in T389078).
When I create an event using Special:EnableEventRegistration
AND the selected namespace is in the list configured in community configuration (T387966)
Then the event will be created successfully.
When I create an event using Special:EnableEventRegistration
AND the selected namespace is NOT in the list configured in community configuration (T387966)
Then the event will be NOT be created successfully
AND an error will be shown with the text below.
When I edit an event using Special:EditEventRegistration
AND the event page namespace is NOT in the list of allowed namespaces
AND I do NOT modify the event page
Then the event will be edited successfully
When I edit an event using Special:EditEventRegistration
AND the event page namespace is NOT in the list of allowed namespaces
AND I modify the event page
AND the new event page is not in a permitted namespace
Then the event will be NOT be edited successfully
AND an error will be shown with the text below.
**Error message**:
- If there is a single permitted namespace: use the standard error, whatever that is (it should mention the name of the allowed namespace, but note that it is buggy for the mainspace: T389083)
- If there are multiple permitted namespaces: `{EventTitle} is not in a permitted namespace.`