refactor: improve SDAP entity add/update flow management

This commit refactors the SDAP entity QoS flow to DRB mapping functionality
to improve code organization and enhance maintainability.

Key changes:
- Split nr_sdap_qfi2drb_map_update into focused functions:
  * nr_sdap_add_qos_flows_to_drb: handles QFI addition to DRB
  * nr_sdap_rm_qos_flows_from_drb: handles QFI removal from DRB
  * nr_sdap_ue_control_pdu_config: handles UE control PDU generation
- Consolidate add/modify logic into reusable nr_sdap_addmod_entity function
- Remove entity existence checking and updating from new_nr_sdap_entity:
  this function should only add SDAP entities
- Improve function separation of concerns: do SDAP entity add or update
  separately and improve modularity by splitting operations in self
  contained functions
- At SDAP creation, do only add of QFI to DRB mapping
- rename new_nr_sdap_entity to nr_sdap_add_entity for function naming consinstency

openair2/RRC/NR/rrc_gNB_nsa.c

@@ -177,7 +177,7 @@ static void rrc_nsa_add_drb(const int ue_id,
     sdap.drb_id = drb->drb_Identity;
     sdap.defaultDRB = true;
     // add SDAP entity (terminated at gNB, since it's EPC)
-    new_nr_sdap_entity(GNB_FLAG_YES, ue_id, sdap);
+    nr_sdap_addmod_entity(GNB_FLAG_YES, ue_id, sdap);
     // add PDCP entity
     nr_pdcp_add_drb(GNB_FLAG_YES, ue_id, drb->pdcp_Config, &sdap, sp);
   }

openair2/RRC/NR_UE/rrc_UE.c

@@ -619,7 +619,7 @@ static void rrc_ue_add_bearer(const int ue_id, const NR_DRB_ToAddMod_t *drb, con
     sdap = nr_sdap_get_config(GNB_FLAG_NO, drb->cnAssociation->choice.sdap_Config, drb->drb_Identity);
   }
   // add SDAP entity
-  new_nr_sdap_entity(GNB_FLAG_NO, ue_id, sdap);
+  nr_sdap_addmod_entity(GNB_FLAG_NO, ue_id, sdap);
   // add PDCP entity
   nr_pdcp_add_drb(GNB_FLAG_NO, ue_id, drb->pdcp_Config, &sdap, sp);
 }