[Vmdb::Settings::Validator] Add .integer_with_method?

This tests that a value in the settings is in fact a integer, or a
integer that can be evaluated via `.to_i_with_method` to something you
would expect.

This becomes challenging because `.to_i` by default will take any
string and convert it to zero.  This means that:

  irb> "".to_i == 0
  true
  irb> "Five".to_i == 0
  true
  irb> "Foobar".to_i == 0
  true

Hence the complexity of the method, since it requires checking that:

- it is something that is a reasonable to expect for an int
- zero when explicitly asked for
- a blank value

lib/vmdb/settings/validator.rb

@@ -31,6 +31,23 @@ def validate
 
       private
 
+      def integer_with_method?(num)
+        if is_integer?(num.to_i_with_method) && num.present?
+          # handling the "Five".to_i == 0 case
+          #
+          # Allows:
+          #
+          #   - 0
+          #   - 0.minutes (always will be zero)
+          #   - any integer
+          #   - any integer + method
+          #
+          num.to_i_with_method != 0 || num.to_s.match?(/^0(?=\..*|$)/)
+        else
+          num.blank?
+        end
+      end
+
       def webservices(data)
         valid, errors = true, []