Support self associations in export mappings

Export mappings do not support objects with self associations.

When trying to export an object through self association "No valid associations available." is raised as error.

A workaround is to retrieve the object by association in a microflow through "by microflow”, which is litterally the same as would happen when choosing by association directly.

"It's in fact something we never intended on supporting before, so it's a known limitation, rather than a bug.”

(Support Ticket ID 129227)