Makes PGP sign-only mails very difficult

Expected behavior

I should have the ability to turn on PGP signatures easily without clicking through a dialog or having to enable an option in the settings, like in earlier versions.

Actual behavior

I have to enable a per-account setting to even have the ability to enable PGP sign-only, and then I have to click through a dialog for each email I send..

Signing email is company policy, and I can't encrypt emails to a mailing list, so nagging me about why it's bad doesn't help; it only irritates me. K-9 didn't previously do this, and it's a bad UI and bad UX.

Steps to reproduce

1. Attempt to sign an email to a mailing list
2. Fumble around for a while
3. Find that there's a new setting in the options that must be enabled
4. Find that the previous checkboxes are no longer present; now a menu is required
5. Enable the option
6. Find that it prompts me with information I already know

Environment

K-9 Mail version:
5.203

Android version:
7.1.1

Account type (IMAP, POP3, WebDAV/Exchange):
IMAP

Start by reproducing the PGP sign-only flow described in the issue on an Android build, including the per-account setting and compose dialog. Trace the account setting and message-compose entry points to identify where signing is enabled and prompted; done means sign-only mail can be enabled without repeated informational dialogs or unnecessary setup.