Action feedback (confirm, unsubscribe, errors)

[NecatiMeral]

Is your feature request related to a problem?

An opt-in confirmation or unsubscription should display a meaningfull message instead of a simple redirect to the Joomla! base address. +1 if those messages can be customized.
This could be used to provide feedback for those actions:

• successful confirmation
• failed confirmation (expired, not-known, already registered)
• unsubscription
• ... you name it

Solution you'd like

A configurable message in the SuperMailer element.

Alternatives you've considered

Configurable URLs to redirect after related actions. Those URLs could contain parameters which can be parsed using custom javascript. But this would not be a turnkey solution.

Additional context

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