Bug 1690681: Generate absolute URLs in emails

[Rob--W]

See https://bugzilla.mozilla.org/show_bug.cgi?id=1690681#c2

I haven't tested this patch, but guess that this may work based on reading code across the https://github.com/mozilla-services/phabricator-extensions, https://github.com/mozilla-conduit/phabricator and https://github.com/mozilla-conduit/phabricator-emails repositories.

[Rob--W]

@mitchhentges Could you review this? I haven't tested it but it should work.

[mitchhentges]

@Rob--W sure thing, I'll take a look 👍
Can you re-create this PR for https://github.com/mozilla-conduit/phabricator instead? We're deprecating this repo soon :)

[mitchhentges]

Tested this locally:

• Revision and user links are generated beautifully
• Project links (e.g.: #bmo-core-security) still have relative links (/tag/bmo-core/security). This is because we tell Phabricator that we want "regularly rendered comments", not "HTML-email rendered comments", and the regularly-rendered-comments don't respect uri.full when handling projects.
  • However, if we switch to have Phabricator generate "HTML-email rendered comments" then we run into other issues, like Phab injecting its own CSS that uses px font sizing rather than relative font sizing. IIRC, there was other reasons why we didn't tell Phab to generate comments specifically for email, but I can't remember what those reasons were 😞. Either way, this is something that we can doctor with a patch to core Phab code. But, since we hardly refer to projects, this isn't a large concern.

To summarize: nice investigation, patch looks good, let's land it once it's targeting mozilla-conduit/phabricator instead of mozilla-services/phabricator-extensions.

[Rob--W]

Moved to mozilla-conduit/phabricator#1

I apparently made the first ever PR/issue on that repo.