R1:d710fc097fb1

Improve messaging and setup process for configuring outbound email.

Summary:
- Make the instructional text generally more useful.
- Show the current configured adapter.
- When the configuration prevents outbound email from being delivered, show a
warning.
- Detect 'curl' extension during setup since it's more-or-less required
- Add curl extension to the install scripts

codeblock: can you verify the rhel-derivs changes are correct?

Test Plan:
Set adapter to test, verified warning; entered setup…