Fix: Store meetup-mf2 event locations correctly

I didn't notice until the other day that RSVPs via meetup-mf2 were rendering with an invalid location.

It appears that this is due to the response from meetup-mf2 coming back correctly as a String[], but being put into my site as a String.

This was originally picked up as part of meetup-mf2!5 but wasn't fully actioned until www-api!104.

The fix in the site is to make sure that we store each location as a String[].

Closes #925 (closed).