String interpolators for volto-absolute-url and volto-portal-url

[erral]

In a Volto project we are working on, we will be using content-rules to trigger some notification messages to end-users. Although the content-rule itself will be configured using the classic front-end, it will be sending and email to some users, and needs to create the proper Volto url in the message, and thus the ${absolute_url} and ${portal_url} string interpolators available in the content-rules can't be used.

We have prepared a ${volto_absolute_url} and ${volto_portal_url} interpolators that use the already existing Volto url coming from volto settings control panel to build the final url.

I think that plone.volto could be the proper place to integrate that code, we can contribute that without much effort. What do you think?

[erral]

With seamless mode these interpolators are not needed, they are only needed when Plone is deployed in a /api like path