Crowdsec: allow customization of the sender address in email notifications

[lucagasparini]

Feature request
It would be very useful to allow administrators to configure a custom sender email address for CrowdSec notifications.

Problem
Currently, the sender address for email notifications cannot be customized. This limitation can cause issues in environments where:

• a specific sender address is required by organizational policies.
• email servers enforce SPF, DKIM, or DMARC rules that must match a designated sending domain.

Proposed solution

• add an option in the module’s advanced settings to configure a custom sender (From) email address.
• provide a way to run a "test email" directly from the interface, so administrators can quickly verify their configuration before going live.

Benefits

• increased flexibility for administrators.
• better integration with existing email infrastructure and security policies.
• easier troubleshooting through the test email function.

See also
Internal discussion: https://mattermost.nethesis.it/nethesis/pl/twusr7mqs7gtffxzgb9rofsygw

[DavidePrincipi]

It would be very useful to allow administrators to configure a custom sender email address for CrowdSec notifications.

This is true for any application!