Merge remote-tracking branch 'origin/rrc-qos-refactor' into integration_2026_w07 (!3907)

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

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)

doc/RRC/rrc-usage.md

@@ -84,7 +84,7 @@ the [MAC configuration](../MAC/mac-usage.md) as well for SIB configuration.
       `0xffffff` is a reserved value and means "no SD"
     Note that: SST=1, no SD is "eMBB"; SST=2, no SD is "URLLC"; SST=3, no SD
     is "mMTC"
-- `enable_sdap` (default: false): enable the use of the SDAP layer. If
+- `enable_sdap` (default: true): enable the use of the SDAP layer. If
   deactivated, a transparent SDAP header is prepended to packets, but no
   further processing is being done.
 - `cu_sibs` (default: `[]`) list of SIBs to give to the DU for transmission.
@@ -94,8 +94,6 @@ the [MAC configuration](../MAC/mac-usage.md) as well for SIB configuration.
 
 - `um_on_default_drb` (default: false): use RLC UM instead of RLC AM on default
   bearers
-- `drbs` (default: 0): the number of DRBs to allocate for a UE, only useful for
-  do-ra or phy-test testing
 
 #### Neighbor-gNB configuration
 

doc/RUNMODEM.md

@@ -544,7 +544,7 @@ sudo ./nr-uesoftmodem --do-ra
 
 #### Run OAI with SDAP & Custom DRBs
 
-To run OAI gNB with SDAP, simply include `--gNBs.[0].enable_sdap 1` to the binary's arguments.
+SDAP is enabled by default. To disable SDAP, include `--gNBs.[0].enable_sdap 0` to the binary's arguments.
 
 The DRB creation is dependent on the 5QI. 
 If the 5QI corresponds to a GBR Flow it assigns a dedicated data radio bearer.