(feat): Unpack extensions into complex function types #8

The more in-depth we use extensions, the more likely is is that we need custom extensions. New `UnpackExtensions` function in the high package makes this easy. Low level models have been updated to support feature fully and docs added in README and examples as well.

Signed-off-by: Dave Shanley <dave@quobix.com>

datamodel/low/v2/parameter_test.go

@@ -207,5 +207,6 @@ allowEmptyValue: true
 	assert.Equal(t, "int", v.Value.A)                          // A is v2
 	assert.True(t, n.GetRequired().Value)
 	assert.True(t, n.GetAllowEmptyValue().Value)
+	assert.Len(t, n.GetExtensions(), 1)
 
 }