I want to , in a loop, add values to an array of hashes in puppet

I have an array of hashes like so:

array => [
  { server_name => $servername, user_name => 'stanley' }
  { server_name => $servername, user_name => 'andy'    }
  { server_name => $servername, user_name => 'jim'     }
  { server_name => $servername, user_name => 'michael' }
  { server_name => $servername, user_name => 'dwight'  }
]

I would like to receive the user_names in an array ($user_names = [stanley,andy,jim,michael,dwight]) as parameter in the class, and then, in a loop, append each hash with only the different user_name. So far I've been trying to do it with the each function, but it doesn't seem to be the way to go.