Disable order owner check for payment if guest checkout is enabled as per #4957
Update error message, making it clear to log in and try again.
Move guest check to wc_customer_has_capability
Should check for yes if guest checkout is enabled
Drop guest checkout test and only check if order is for guest
Merge pull request #4960 from kloon/tweak_guest_checkout_pay_link

Disable order owner check for payment link if guest checkout enabled