Update email alert design based on the new frontend design

[siccovansas]

The email alert should present a document in the same way as a document 'card' in the new frontend design.

The subject of the email alert should also use the newly available 'name' of an alert instead of only the query.

[coret]

• Maybe use the service name in sender, instead of Open State Foundation <[email protected]>

• The "Alert voor ** stopzetten" text is a poorly formatted link and very close to the document link. Especially on mobile a mis tap on either could happen easily. Maybe make it a bigger red CTA button, with enough space from other links.

• When I received an alert today, I had an urge to add another monitor. But there is no CTA link/button to add a monitor. Clicking the document shows the Bron page for a short time but redirects to the source document. The URL of the service https://bron.live/ isn't part of the email.

[Coretteket]

+1 for @coret's notes on the unsubscribe links. We should probably require a confirmation on the unsubscribe page, or at least send a confirmation mail about the unsubscribing so that it doesn't go unnoticed.