RRC QoS refactor: PDU Session Modify support, SDAP fixes, and code improvements

Guido Casatirequested to merge
rrc-qos-refactor into develop

The goal of this MR is to prepare the RRC/NGAP layer for the multi-QoS support. The MR:

  • enables PDU Session Resource Modify support in RRC/NGAP/E1AP
  • fixes SDAP header mapping
  • enables SDAP by default
  • refactors QoS flow handling in RRC/NGAP
  • improves error handling, and code maintainability in RRC/NGAP

Changes:

  • NGAP PDU Session Modify:
    • add NGAP PDU Session Resource Modify Request/Response handling with proper error reporting for unrecognized sessions and AMF UE NGAP ID validation
  • E1AP Bearer Context Modification:
    • add DRB To Remove List IE to support DRB release during modify
    • rename numQosFlow2Setup to numQosFlowsMod in DRB To Modify List
  • RRC QoS flow handling:
    • enable multi-QoS flow support per DRB
    • add utilities to map NGAP QoS parameters to E1AP
    • filter QoS flows by DRB ID
  • SDAP configuration:
    • Fix SDAP header UL/DL mapping between internal representation and ASN.1 enum (invert mapping)
    • change SDAP header fields from long to bool for clarity
  • F1 DRB setup refactoring:
    • Extract shared helpers for F1 DRB setup list filling
    • reduce duplication between E1 response and direct DRB setup paths
  • AMBR management:
    • Store AMBR in UE context
    • validate AMBR is set before bearer setup
  • Configuration:
    • remove unused drbs configuration parameter
    • enable SDAP by default (change default from false to true)

Ref: 3GPP TS 38.413

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