[scenario-11 hermes] alice writes M1 on node-1
[scenario-11 hermes] bob writes M2 on node-2
[scenario-11 hermes]   M1=b01a7380-6fa5-4ed5-bb1f-0f134e0056b4 M2=d069ab93-e247-4694-941d-75ff4181691f
[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)