Strongly type "type" property of Field

[RhysSullivan]

Rather than having the type of "type" Field be of type string, it should be 'INT8' | 'INT16' | ... | string to make it easier to infer what type to check

[hiSandog]

The scope would be easier to review if the first version defined a small acceptance contract for Strongly type "type" property of Field. I would call out the default behavior, the migration/backwards-compatibility story, and one or two cases that are intentionally out of scope so the implementation does not grow beyond the original request.