like-service

create : {
  contentId: 'fefewfew',
  userId: [optional]
}

get : contentId, userId
[{
  contentId: 'blah'
  count: 10,
  userLiked: true
}]

get : [contentId, contentId], userId
[{
  contentId: 'blah'  
  count: 10,
  userLiked: true
},
{
  contentId: 'blah'
  count: 10,
  userLiked: true
},
{
  contentId: 'blah'
  count: 10,
  userLiked: true
},
{
  contentId: 'blah'
  count: 10,
  userLiked: true
}]

User cant like content more than once