erp5_pdm: add default Link sub document on a supply line

5 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:14:04

passed ERP5.PerformanceTest-Master

00:32:57

passed ERP5.UnitTest-Master

02:03:55

passed SlapOS.Eggs.UnitTest-Master.Python2

00:24:13

passed SlapOS.Eggs.UnitTest-Master.Python3

00:38:20