ok I ended up using the transformRequest on the $resource definition, something like bellow:
return $resource('/user', {}, {
login: {
url: 'user/login',
method: 'PUT',
headers: {
'Content-Type': 'application/json',
'Accepts': 'application/json'
},
transformRequest: function(data) {
data.OsModel = Os.model;
data.OsVersion = Os.version;
return JSON.stringify(data);
}
}
});
not sure if thats the most elegant way but this is working for me.