Support alternate metadata tags alongside canonical

[ianleeder]

I'm not sure how this would be presented/useful via the backoffice, but I could use it right now in the AfterMetaTagsNotification handler.

Right now we can generate meta tags to set the canonical URL:

<link rel="canonical" href="https://www.mysite.com/en-au/"/>

The standard also supports alternate links based upon multiple factors, including language. I need to generate the following:

<link rel="alternate" href="https://www.mysite.com/en-au/" hreflang="en-au"/>
<link rel="alternate" href="https://www.mysite.com/en-nz/" hreflang="en-nz"/>

This would be simple to do in the AfterMetaTagsNotification handler.

As for how it could be implemented in the backoffice? I'm not sure I am qualified to answer that, as the legacy project I'm working on has hacked cultures and hostnames to work in a non-standard fashion. I haven't done it properly in Umbraco. My only thought would be some sort of string matching/replacement.

Alternate URL rules

• Replace URL <regex> with <url_lang> for language <lang_code>
• Replace URL \/en-\w{2,3} with en-au for language en-au
• Replace URL \/en-\w{2,3} with en-nz for language en-nz

My case is somewhat simple, but it could be more complex like replacing .com.au with .co.nz