Add purge method to Shop::Credit, tests.

lib/WebGUI/Shop/Credit.pm

@@ -35,7 +35,8 @@ readonly userId => my %userId;
 
 =head2 adjust ( amount, [ comment ] )
 
-Adjusts the amount of credit this user has by a specified amount.
+Adjusts the amount of credit this user has by a specified amount.  Returns 0 if the current user is Visitor.
+Otherwise, returns the amount set.
 
 =head3 amount
 
@@ -154,6 +155,20 @@ sub new {
 
 #-------------------------------------------------------------------
 
+=head2 purge ( )
+
+Removes all shop credit for the current user.
+
+=cut
+
+sub purge {
+    my ($self) = @_;
+    $self->session->db->write("delete from shopCredit where userId = ?",[$self->userId]);
+    return 1;
+}
+
+#-------------------------------------------------------------------
+
 =head2 session () 
 
 Returns a reference to the current session.