title: How to properly initialize documents in mongoose collection
body: <p>Please, correct me if my design is not recommended:</p>
  
  <p>I have a model for blog posts with a field "category". I want the user to be able to type the category (with typeahead) and, if the category isn't there, the user would be able to create it. However, in order to prevent unorganized entries, I want to populate the field "category" with a list of categories. </p>
  
  <p>Question is, should I use field "category" as an array or as a sub-document referenced to another model called "Category"? I am assuming the latter would be the recommended design, because it avoids code replication and makes easy the interaction necessary for the user to add a new category. </p>
  
  <p>Now, if I use it with sub-documents, how could I initialize the model "Category" with a list of categories on server startup? </p>