allow to define custom canonical urls : enhancement

[Hari-Bonda]

Hello, we want to use flarum as a commentator on a static page. for the same, we will be embedding flarum discussion. this may cause duplicate content on two different pages, so we just want to mention that the discussion URL is canonical to the original blog post URL .

allow us to define a custom canonical URL so where can mention the blog post URL as the main URL

example page https://blog.codinghorror.com/what-does-stack-overflow-want-to-be-when-it-grows-up/#discourse-comments

https://ghost.org/integrations/discourse/