Valkyrie::Types::Strict::DateTime broken?

[hcayless]

I've found that I can't use the strict version of DateTime because various bits of conversion code use .utc to coerce to the UTC timezone (e.g. https://github.com/samvera/valkyrie/blob/master/lib/valkyrie/persistence/shared/json_value_mapper.rb#L155). Unfortunately, that results in the value being converted to a Time, which then promptly fails the strict checking because it's not a DateTime. It could probably be fixed by replacing calls to .utc with .utc.to_datetime.

I can work up a pull request if that's desirable.

[tpendragon]

@hcayless Good catch! We don't use strict types much personally, so I'm glad someone's exercising that bit. I'd love a pull request! Thank you.