Allow adding additional authors via ACF fields

[thomaslow]

Currently, authors are only extracted from the post author and additional co-authors via the co-authors-plus plugin. Co-authors may also be provided by custom acf fields.

[errotu]

At Völkerrechtsblog, co-authors are added as a custom taxonomy called "authors". They can be retrieved, for example, as follows (from the citationMeta code snippet currently integrated in our functions.php):

// Retrieve the authors (adjust custom field or function to retrieve the array of authors correctly, e.g. for CoAuthors Plus get_coauthors())
	$citationAuthors = get_field('authors');

<?php if($citationAuthors) :
foreach($citationAuthors as $author ): 
	// Adjust "name" if necessary, e.g. for CoAuthors Plus: display_name 
	?>
	<meta name="citation_author" content="<?php echo $author->name; ?>">	
<?php endforeach;