This allows users of `FieldError` to be able to query information about
the struct the field is contained within. This information can then be
used to work out what to display when the param field points to another
field, such as with `gtfield`, and a tag name function has been
registered.
This fixes a few documentation issues I noticed.
- Explain what Func is supposed to return.
- Remove change reference to ActualNamespace to mention StructNamespace
instead.
- Remove references to Validatable, which no longer exists.
- Fix godoc formatting.
- Delete extra text from ReportValidationErrors comment.
- Change ReportError interface definition so its arguments are named
consistently with what they do.
Running goimports on the codebase deletes all the imports of "github.com/go-playground/universal-translator".
The fix consists of explicitly qualifying the import statements with ut.