Feature Request: Default superuser email points to a public mailbox (security risk) + request for admin email API

Description:
When creating the Dataverse superuser during the initial setup, the system automatically assigns the following email address: dataverse@mailinator.com.
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This is a potential security vulnerability, because mailinator.com is a public mailbox service — anyone can access emails sent to that address without authentication.
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As a result, an attacker who knows this default email could easily initiate a password reset and take over the Dataverse superuser account on instances where the administrator didn’t change the default email after installation.

Expected Behavior:
The superuser email should either:

• Require a custom email to be provided during setup, or
• Default to a placeholder that is clearly invalid (e.g. changeme@example.com) to prompt immediate replacement.

Proposed Solutions:

• Change the default superuser email to a non-functional placeholder, or enforce a prompt during setup to specify a valid administrator email address.
• Add an API endpoint to allow administrators to securely change the superuser/admin email address via curl.

This would improve automation and security management, by enabling scripted rotation or correction of the admin email without relying on manual UI operations.
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See also https://groups.google.com/g/dataverse-community/c/mLEdP8p24RM/m/KIIrqE-4BAAJ

Start at the initial setup flow that assigns dataverse@mailinator.com and trace the existing administrator email and password-reset handling. Decide how setup should require or mark a non-functional address, and define the secure API behavior for changing it; done means the public mailbox is no longer used and the change path is covered by appropriate tests.