Attribute types should be strict

[awead]

The upcoming dry-types release will default to strict data types. We ought to define all our attributes as strict to make upgrading easier.

https://dry-rb.org/news/2019/04/23/dry-types-and-dry-struct-1-0-0-released/

Alternatively, we could try upgrading to dry-types 1.0 now, but I don't think the current Valkyrie version supports it. Because Valkyrie 2.0 is already a release candidate, the update to dry-types may not happen until 3.0 is out.

We should definitely consider doing this before any production data goes in. If we move to production, and there is inconsistent data typing, such as strings vs. arrays, or dates vs. strings, we would need to migrate any non-conforming data to its proper type before we could update these gems.

[awead]

TODO:

• this may be done already as part of Valkyrie 2.0
• investigate if we should do this now
• do it if it isn't too work intensive