Convert param input to String

The ruby AWS SDK always expects string input. Even if your
cloudformation parameter type is `Number`, it still wants it to be a
ruby String. The validation of parameter value will happen in
cloudformation land.

Currently stackup is just passing through the raw YAML value to the SDK
as is - which means it is up to the caller to understand the nuances on
the ruby AWS SDK (where everything must be a string). Given stackup is
supposed to "help" reduce cognitive load, I think it's ok for it to help
convert our YAML values in this instance.

lib/stackup/parameters.rb

@@ -45,7 +45,7 @@ def to_a
           if value == :use_previous_value
             record[:use_previous_value] = true
           else
-            record[:parameter_value] = value
+            record[:parameter_value] = value.to_s
           end
         end
       end
@@ -75,7 +75,7 @@ def value
       if use_previous_value
         :use_previous_value
       else
-        parameter_value
+        parameter_value.to_s
       end
     end
 

spec/stackup/parameters_spec.rb

@@ -146,6 +146,30 @@
 
     end
 
+    context "with Integer values" do
+
+      let(:input_records) do
+        [{ :parameter_key => "SomeInteger", :parameter_value => 123_456_789 }]
+      end
+
+      subject(:parameters) { Stackup::Parameters.new(input_records) }
+
+      describe "#to_hash" do
+        it "converts the Integer to a String" do
+          expected = { "SomeInteger" => "123456789" }
+          expect(parameters.to_hash).to eql(expected)
+        end
+      end
+
+      describe "#to_a" do
+        it "converts the Integer to a String" do
+          expected = [{ :parameter_key => "SomeInteger", :parameter_value => "123456789" }]
+          expect(parameters.to_a).to eql(expected)
+        end
+      end
+
+    end
+
     context "with empty parameter file" do
 
       let(:input_records) { false }