send_password_reset_email: Add a flag to only email users who need it.

Emailing the password reset email to users who have already logged in
is not as useful.

help/include/import-how-users-will-log-in.md

@@ -62,6 +62,13 @@ If you imported your organization into Zulip Cloud, simply e-mail
      ./manage.py send_password_reset_email -r <subdomain> --all-users
      ```
 
+   If you would like to only send emails to users who have not logged in yet,
+   you can use the following variant instead:
+
+     ```
+     ./manage.py send_password_reset_email -r <subdomain> --all-users --only-never-logged-in
+     ```
+
 {end_tabs}
 
 ### Manual password resets

zerver/management/commands/send_password_reset_email.py

@@ -17,6 +17,11 @@ class Command(ZulipBaseCommand):
 
     @override
     def add_arguments(self, parser: ArgumentParser) -> None:
+        parser.add_argument(
+            "--only-never-logged-in",
+            action="store_true",
+            help="Filter to only users which have not accepted the TOS.",
+        )
         parser.add_argument(
             "--entire-server", action="store_true", help="Send to every user on the server. "
         )
@@ -43,6 +48,11 @@ class Command(ZulipBaseCommand):
                         "You have to pass -u/--users or -a/--all-users or --entire-server."
                     )
                 raise error
+        if options["only_never_logged_in"]:
+            users = users.filter(tos_version=-1)
+
+        if not users.exists():
+            print("No matching users!")
 
         self.send(users)