Make custom domain canonical when viewing in .appspot.com

Question

I'm using wordpress on app engine. I connected my custom domain, but of course the site is also available in app-id.appspot.com. I want to make my custom domain the canonical url. Usually, in wordpress, SEO plugins create the canonical domain from the site url setting, but in app engine this setting is not editable, but set dynamically according to the host you use to view the site.

So, in short, what's the best solution to create a canonical meta tag in wordpress under app engine?

Answer 1

My solution for now is disabling the canonical tag created by the SEO plugin, and insert my own tag in header.php with the right domain hardcoded.