Feature/public id sync

[DavidCramer]

Allows for being able to alter the public_id for uploading as well as correcting the folder changing sync.

Testing notes.

This allows for changing the public ID of assets.
Below is an example of using the filter cloudinary_upload_options to use the assets slug as it's public_id
Add the snippet in the functions.php in your theme.
go to the media library page. If all assets slug is the same as the ID (it should be), then the cloud should be green.

Edit an asset, and change the slug (you may need to select Screen Options, and enable it).
Update and go back to the media library. The image should now be in the syncing state (orange cloud).
After a moment, it should be green and the public ID should be the same as the slug.

	add_filter( 'cloudinary_upload_options', function ( $options, $attachment_post ) {

		/**
		 * Structure of options as follows:
		 *
		 * $options = array(
		 *    'unique_filename' => false, // Allow for auto filenames. See Cloudinary docs.
		 *    'resource_type'   => $resource_type, // Type can be 'image' or 'video' or custom.
		 *    'public_id'       => $public_id, // Changing this will change the public ID as stored in Cloudinary.
		 *    'context'         => array(
		 *        'caption' => esc_attr( $post->post_title ), // Set the caption data in Cloudinary.
		 *        'alt'     => $post->_wp_attachment_image_alt, // set the alt text of the asset in Cloudinary
		 *    ),
		 * );
		 **/

		// To change the asset public_id.
		$post_name = strtolower( $attachment_post->post_name );
		if ( $post_name !== $options['public_id'] ) {
			$options['public_id'] = $post_name;
		}

		return $options;
	}, 10, 2 );

[parabrola]

Looks like a good refactor overall, with solid changes, but there's some unclarity that should be addressed before this PR moves forward.

[parabrola]

Maybe we can switch to this in order to satisfy linters:

Suggested change

	if ( false !== strpos( $public_id, '/' ) ) {
	// Split the public_id into path and filename to allow filtering just the ID and not giving access to the path.
	$public_id_info = pathinfo( $public_id );
	$public_id_folder = trailingslashit( $public_id_info['dirname'] );
	$public_id_file = $public_id_info['filename'];
	} else {
	// File is in the root of cloudinary.
	$public_id_folder = '';
	$public_id_file = $public_id;
	}
	// File is in the root of cloudinary.
	$public_id_folder = '';
	$public_id_file = $public_id;
	if ( false !== strpos( $public_id, '/' ) ) {
	// Split the public_id into path and filename to allow filtering just the ID and not giving access to the path.
	$public_id_info = pathinfo( $public_id );
	$public_id_folder = trailingslashit( $public_id_info['dirname'] );
	$public_id_file = $public_id_info['filename'];
	}

[DavidCramer]

@dugajean Nice idea. I usually do prefer to have a default, and if it's not what's expected then change.

[parabrola]

LGTM

[pereirinha]

Thanks, @DavidCramer for the hard work on this one.