title: Rails migration create_join_table with uuids
body: <p>Newer versions of rails let you specify that tables should be created with a uuid primary key like so:</p>
  
  <pre><code>create_table :foos, id: :uuid do |t|
    # ...
  end
  </code></pre>
  
  <p>Which is great.  And for a long time rails has supported creating join tables like so:</p>
  
  <pre><code>create_join_table :foos, :bars do |t|
    # ...
  end
  </code></pre>
  
  <p>Also great.  Except my tables have uuid primary keys and that generates foreign key columns of type integer instead of type uuid.</p>
  
  <p>Looking over <a href="http://apidock.com/rails/v4.2.1/ActiveRecord/ConnectionAdapters/SchemaStatements/create_join_table" rel="noreferrer">the documentation for <code>create_join_table</code></a>, I can't find anything obvious to change the column type.  Is it possible to use <code>create_join_table</code> with uuids?</p>
  
  <p>Or do I have create the join table manually:</p>
  
  <pre><code>create_table :bars_foos, id: false do |t|
    t.uuid :bar_id
    t.uuid :foo_id
  end
  </code></pre>