FIX Reenable indexing of relationship fields
FIX Reenable indexing of relationship fields

In previous versions one could add e.g. a filter field for their index to
a relationship, such as 'Categories.ID' where categories is a many_many
relationship. This stopped working in the SS4 upgrade. Namespaces, whoop.

silverstripe-labs/silverstripe-fulltextsearch,dnadesign/silverstripe-fulltextsearch,dnadesign/silverstripe-fulltextsearch