Use template variable to add or remove swap button.

Use template variable to add or remove swap button.

In combination with email notifications this button can be dangerous - ie an accidental click and
a donor rather than a staff member gets the email.

My thinking is to disable this via the activity assignee extension,
https://lab.civicrm.org/extensions/assignee/-/issues/2 - but it's cleaner for
an extension to intervene by setting a smarty variable than using javascript
to remove the button and I feel like it makes more sense for the form to
assign 'instruction variables' than for the decision to freeze to
also have 'hidden' effects further down