Allow user authentication from email links

[nicoolas25]

Summary

Note: this PR replaces #858

As part of #829 I would like to authenticate users right from emails. This PR sets the foundations to do this.

So far we authenticated users using matches' tokens or slot_alerts's tokens.
Now we need users' tokens: we need communication unrelated to any of the above events.

Details

No functional changes should be part of this PR.

It adds a concern for controllers UserAuthenticationViaSignedId that complements the usual devise/warden authentication using an authentication_token based on globalid.

It creates a single partial to DRY those routes:

• users#destroy,
• matches/users#destroy, and
• slot_alerts/users#destroy.

Also DRY those views:

• slot_alerts/users#edit, and
• matches/users#edit

... into users/_confirm_destroy_message.

The goal is to reuse confirm_destroy_profile_path from email and sign it with an authentication token.

This users#confirm_destroy action looks like this:

Poke @mininao as you authored the original issue.

The next steps are:

1. Create the rake task to identify the appropriate users
2. Create emails to send to those users, include a link to confirm_destroy_profile_path with an auth token
3. Reuse that in matches's emails (and slot_alers's ones) when offering the user the ability to remove themselves from the list

[nicoolas25]

@EmCousin Approved the PR here.

[mathieuripert]

Nice :)