code: public static ForeignKeyConstraint of(String name, Attribute attribute, Attribute reference) {
  		return new Builder((DatabaseRelationDefinition)attribute.getRelation(), 
  							(DatabaseRelationDefinition)reference.getRelation())
  									.add(attribute, reference).build(name);
  	}
docs: creates a single-attribute foreign key
  
  @param name
  @param attribute
  @param reference
  @return