ProjectPermissionController: make sure groups don't exist before creating them
ProjectPermissionController: make sure groups don't exist before creating them

Adding logic to check for a group by external ID, before trying to create it.

Shaxine/kanboard,renothing/kanboard,thylo/kanboard,lianguan/kanboard,patoi/kanboard,xavividal/kanboard,oliviermaridat/kanboard,lianguan/kanboard,patoi/kanboard,thylo/kanboard,Nerdingher/kanboard,Nerdingher/kanboard,Shaxine/kanboard,fguillot/kanboard,BlueTeck/kanboard,cdgeelen/kanboard,kanboard/kanboard,lianguan/kanboard,xavividal/kanboard,stinnux/kanboard,fguillot/kanboard,cdgeelen/kanboard,filhocf/kanboard,kanboard/kanboard,vaikan/kanboard,libin/kanboard,vaikan/kanboard,BlueTeck/kanboard,djpadz/kanboard,kanboard/kanboard,cdgeelen/kanboard,renothing/kanboard,Busfreak/kanboard,filhocf/kanboard,libin/kanboard,djpadz/kanboard,fguillot/kanboard,Nerdingher/kanboard,Busfreak/kanboard,thylo/kanboard,BlueTeck/kanboard,stinnux/kanboard,renothing/kanboard,vaikan/kanboard,Shaxine/kanboard,xavividal/kanboard,Busfreak/kanboard,filhocf/kanboard,djpadz/kanboard,oliviermaridat/kanboard,patoi/kanboard,stinnux/kanboard,oliviermaridat/kanboard