Import: Attachments

[derpixler]

Implement attachment import.

Example on how to use wp_handle_sideload(): http://wordpress.stackexchange.com/a/36083/31323 (the answer shows the usage of media_handle_sideload() but the structure of the parameter is identical to the one for wp_handle_sideload().

• Update W2M\Import\Type\ImportPostInterface:

namespace W2M\Import\Type;

interface ImportPostInterface {

    /**
     * ...
     */

    /**
     * @return string
     */
    public function remote_attachment_url();

}

• Implement the new method in W2M\Import\Type\WpImportPost.
• Parse <wp:attachment_url> in W2M\Import\Service\WpPostParser if exists. Propagate an error if it not exists and the post is of type attachment.
• Update W2M\Import\Service\WpPostImporter to handle the file:
  • Download the file to a temporary file
  • »Handle sideload«
  • Import relevant metadata (but skip these, that pointing to data structures of the remote system like _wp_attached_file if we cannot force a 1:1 mirror of the file paths of the remote system)
  • delete the temporary file