[Task]: Consider no longer accepting email-like add-on IDs (GUIDs) for new add-ons

[willdurand]

Description

Let's consider no longer accepting email-like add-on IDs (GUIDs) for new add-ons since these IDs are, despite being used only for technical purposes, mistaken for real email addresses sometimes, and it's confusing.

Acceptance Criteria

see above

┆Issue is synchronized with this Jira Task

[diox]

This would be a simple change but it has lots of repercussions. There are a lot of documentation to update, potentially developers to warn etc. And we'd still have the existing to care about.

Maybe just updating some documentation and adding a warning in the linter to reduce confusion would be a good start.

[wagnerand-moz]

I'd be in support of this. And even go further and disallow regular developers to specify an add-on ID. It would be auto-generated by AMO on add-on creation.

One exception from this is probably needed for privileged add-ons which are signed outside of AMO, so we'd still need a reserved ID namespace for them.