Settings keys like api_key were shared across providers, so switching
from e.g. Postmark to SendGrid showed the old API key. Now each
adapter gets its own namespaced key (email_postmark_api_key, etc.)
so credentials persist independently and switching back pre-fills
previously saved values.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Card radio component for picking email providers (SMTP, SendGrid, Mailjet, etc.)
with instant client-side switching via JS hook. Adapter configs are pre-rendered
and toggled without a server round-trip. Secrets are preserved when re-saving
with blank password fields. Includes from address field, test email sending,
and disconnect flow.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
