feat: implement PUT for inventory UPF

[patriciareinoso]

Description

This PR depends on #279

This PR implements the edition of UPFs

• Create an index over hostname for UPFs to guarantee unique hostnames in DB

• Create an index over name for gNBs to guarantee unique gNB names in DB

• Modify POST operation to remove the target from path: now hostname and port are specified in the body of the request.

• We cannot create 2 UPFs with the same hostname.

• Add PUT operation:

  • If the UPF hostname does not exist it is created.
  • If the UPF hostname exists, it is modified.
  • Edition of UPF is propagated to Network slices containing a UPF with the given name using a PATCH operation to modify only the UPF field.

• The POST and PUT handlers do not use the config channel -> reduce complexity.