Generate a token and add the parameter to the link.

automatic-login-impl.rb.diff

diff --git a/app/mailers/reservation_mailer.rb b/app/mailers/reservation_mailer.rb
index 4ee2db4..0f8faf2 100644
--- a/app/mailers/reservation_mailer.rb
+++ b/app/mailers/reservation_mailer.rb
@@ -16,6 +16,8 @@ class ReservationMailer < CameraLendsMailer

   def reservation_request_lender(reservation)
     @reservation = reservation
+    @owner = reservation.item.owner
+    @owner.new_token!
     item = reservation.item.decorate
     mail to: reservation.item.owner.email_for_mailer,
          subject: "Reservation request for #{ item.display_name }"
diff --git a/app/views/reservation_mailer/reservation_request_lender.html.haml b/app/views/reservation_mailer/reservation_request_lender.html.haml
index b3ff043..54f4712 100644
--- a/app/views/reservation_mailer/reservation_request_lender.html.haml
+++ b/app/views/reservation_mailer/reservation_request_lender.html.haml
@@ -47,7 +47,7 @@
   okay, but don't leave #{ renter.first_name } hanging!

 %p
-  = btn_email 'Respond now »', reservation_url(@reservation)
+  = btn_email 'Respond now »', reservation_url(@reservation, token: @owner.token)

 %p
   Easy-peesy. After accepting, the renter will pay to finalize the