fix custom grant handler template
<SupportedGrantType>
<GrantTypeName>{{grant_type.name}}</GrantTypeName>
<GrantTypeHandlerImplClass>{{grant_type.handler_class}}</GrantTypeHandlerImplClass>
+ <GrantTypeHandlerImplClass>{{grant_type.grant_validator}}</GrantTypeHandlerImplClass>
{% for key,value in grant_type.properties.items() %}
<{{key}}>{{value}}</{{key}}>
{% endfor %}
