[scenario-11 hermes] alice writes M1 on node-1
[scenario-11 hermes] bob writes M2 on node-2
[scenario-11 hermes]   M1=67b3755f-6e7b-4716-8602-381277e87c31 M2=bdb16417-610f-475f-8543-4da419940967
[scenario-11 hermes] alice links M1 -> M2 with relation=related_to
[scenario-11 hermes]   link POST returned HTTP 201
[scenario-11 hermes] charlie queries links of M1 on node-3
[scenario-11 hermes]   charlie sees M1->M2 link: 1 (expected >=1)