Indicates that a class annotated with this annotation contains constants that should be exported
as Soy Globals.
There are several restrictions imposed on such a class with constants:
- a class cannot be an interface or an annotation;
- inheritance of such classes is prohibited and, thus, classes must be declared with the
"final" declared class;
- constructors or methods are not allowed;
- only constant fields are allowed;
- only primitive and string types are allowed for constant values.
The constants are exported in the namespace of the implementing class.