Add support for creating a NimBLEClient from a NimBLEServer peer.

This allows the NimBLEServer instance to create a NimBLEClient instance to read/write form/to a connected peer.
Only one instance is supported subsequent calls will overwrite the previous client connection information and data.

src/NimBLEServer.h

@@ -48,6 +48,9 @@ class NimBLEExtAdvertising;
 # else
 class NimBLEAdvertising;
 # endif
+# if defined(CONFIG_BT_NIMBLE_ROLE_CENTRAL)
+class NimBLEClient;
+# endif
 
 /**
  * @brief The model of a BLE server.
@@ -77,6 +80,12 @@ class NimBLEServer {
     void                  advertiseOnDisconnect(bool enable);
     void                  setDataLen(uint16_t connHandle, uint16_t tx_octets) const;
 
+# if defined(CONFIG_BT_NIMBLE_ROLE_CENTRAL)
+    NimBLEClient* getClient(uint16_t connHandle);
+    NimBLEClient* getClient(const NimBLEConnInfo& connInfo);
+    void          deleteClient();
+# endif
+
 # if CONFIG_BT_NIMBLE_EXT_ADV
     NimBLEExtAdvertising* getAdvertising() const;
     bool                  startAdvertising(uint8_t instanceId, int duration = 0, int maxEvents = 0) const;
@@ -115,6 +124,10 @@ class NimBLEServer {
     std::vector<NimBLEService*>                            m_svcVec;
     std::array<uint16_t, CONFIG_BT_NIMBLE_MAX_CONNECTIONS> m_connectedPeers;
 
+# if defined(CONFIG_BT_NIMBLE_ROLE_CENTRAL)
+    NimBLEClient* m_pClient{nullptr};
+# endif
+
     static int  handleGapEvent(struct ble_gap_event* event, void* arg);
     static int  handleGattEvent(uint16_t connHandle, uint16_t attrHandle, ble_gatt_access_ctxt* ctxt, void* arg);
     static int  peerNameCB(uint16_t connHandle, const ble_gatt_error* error, ble_gatt_attr* attr, void* arg);