WordPress + Mailgun plugin - Apply Template to all WordPress mail

mailgun-api-force-template.php

<?php

/*
  This code with conjunction of Wordpress Mailgun plugin will force all wordpress mails to apply mailgun wordpress to all mail,
  This could be easy way to beautify emails.
  
  use {{subject}} {{text}} or {{{html}}} - see that html has triple {{{ in order to use raw content and not escape special chars
  
*/
add_filter( 'mg_mutate_message_body', function( $body ) {
	$body[ 'template' ] = 'wordpress';
	$vars = [];
	$vars[ 'subject' ] = $body[ 'subject' ];
	$vars[ 'text' ] = $body[ 'text' ];
	$vars[ 'html' ] = !isset( $body[ 'html' ] ) || !$body[ 'html' ] ? nl2br( $body[ 'text' ] ) : null;
	$vars[ 'body' ] = isset( $vars[ 'html' ] ) && $vars[ 'html' ] ? $vars[ 'html' ] : $vars[ 'text' ];
	$body[ 'h:X-Mailgun-Variables' ] = json_encode( $vars );
	return( $body );	
}, 100 );