Emit enum array as a string under postgres/cockroach

[alii]

Fixes #107

[isaac-sec]

This change is marked as a patch-level change, but it's a breaking change and my existing code now fails to compile.

The pg limitation with custom types (and especially enum arrays) is well known, so I've been using to_json and other JSON functions to convert to JSON in order to get an actual array of the enum type, but now this is erroneously typed by default as a string instead.

Additionally, because the column is typed as string the import of the enum type is now unused and I have to add an exclusion to "declared but never used" rule for the generated types or post process the file after generation, both of which I'd like to avoid.

Can we please revert this change or find a way to fix these issues? Thanks in advance!