Extend M6 client API to allow Media Session Handler lookup table to be updated by 5GMS-Aware Application

[dsilhavy]

Feature description In the Media Session Handler we currently use a lookup table that maps a mediaPlayerEntry to a provisioningSessionId. The provisioningSessionId is required to request the serviceAccessInformation via Interface M5d.

The idea behind this feature request is to allow the 5GMSd Aware Application to update this lookup table via M6d. As a result, the 5GMSd Aware Application can pass <provisioningSessionId, mediaPlayerEntry> entries received via M8d to the Media Session Handler.

[rjb1000]

Note that the third missing piece of the jigsaw -- the host name of the 5GMS AF -- also needs to be known to the Media Session Handler. SA4 is current debating how best to achieve this: see 5G-MAG/Standards#42.

Options under consideration:

1. 5GMS host name at M5 passed back to the 5GMS Application Provider via M1 at provisioning time and then passed via M8 and then M6 to the Media Session Handler
   • This could be part of the API that is the subject of this issue.
   • This solution is not ideal because the 5GMS AF host name at M5 is different for every deployed 5GMS System, and so the 5GMS Application Provider has to detect which deployment the client is in and supply the correct 5GMS AF host name at M8.
2. Well-known 5GMS host name at M5 that is the same in all 5GMS System deployments (e.g. af.ms.3gpp.org).
   • This could be hard-coded into the Media Session Handler.
   • Doesn't work for the case where the 5GMS AF is deployed outside the Trusted DN.
3. Register the 5GMS host name at M5 in the NRF.
   • Not yet clear how this might work for the case where the 5GMS AF is deployed outside the Trusted DN.
   • Requires liaison with SA2, which "owns" the NRF specification.