But i got the error that the types were different, think it was field.endpointtype. What is this, and how do i get it in the addParameterDefinitions, what type does the authority.ftl return, a string? I assume that you can use AuthorityService afterwards to get the group name or something similar.
final NodeRef group =(NodeRef) action.getParameterValue(PARAM_GROUP_NAME);// your parameter should be simply PARAM_GROUP, as there is no real name in it Map<QName, Serializable> groupProperties = nodeService.getProperties(group);
And then you can read the property you want from the groupProperties object.
I have not tested the code, but I guess you will be able to fix it if required.