Add serialize metadata to domain.locales field

[colemanw]

Overview

Adds a bit of metadata to help APIv4 serialize/unserialize this field correctly.

Before

Domain.locales would come back as a string with funny characters.

After

Standardized to array.

Comments

I think leaving it off was just an oversight.

[civibot]

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[eileenmcnaughton]

test this please