title: ActiveStorage::Attachment find resource by blob_id
body: <p>I have the following model</p>
  <pre><code>class Document
    has_many_attached :previews
    ...
  end
  </code></pre>
  <p>And I'm trying to find single elements there.
  The problem is if I do:</p>
  <pre><code>@document.previews.find_by(blob_id: 22)
  </code></pre>
  <p>I get this error: <code>undefined method `find_by' for #&lt;ActiveStorage::Attached::Many&gt;</code></p>
  <p>So I'm kind of forced to loop through enumerable:</p>
  <pre><code>@document.previews.find { |p| p.blob_id == 22 }
  </code></pre>
  <p>Is there any other (better/prettier) way to do this?</p>