feat: common pair function

Do bluetooth pairing and device paring from module.
Lite is not need special pairing.
S3 is require sending pair command.
connect/disconnect routine moved to main class.
We have to use private methods _writeCmd and _waitResp, because 'Already Paired' is error from bluepy point of view
  and it drop connection in this case. So have to simulate _mgmtCmd to avoid disconnect if device already paired via bluetooth.

Author: IATkachenko

tion_btle/lite.py

@@ -285,3 +285,7 @@ def encode_state():
             [encode_state(), sb, tb, int(request["heater_temp"]), int(request["fan_speed"])] +
             self.__presets + lb + [0x00] + self.CRC
         )
+
+    def _pair(self):
+        """Lite is not require special pairing procedure"""
+        return

tion_btle/s3.py

@@ -53,15 +53,9 @@ def __try_get_state(self) -> bytearray:
         _LOGGER.debug("Response is %s", bytes(response).hex())
         return response
 
-    def pair(self):
-        _LOGGER.setLevel("DEBUG")
-        _LOGGER.debug("Pairing")
-        _LOGGER.debug("Connecting")
-        self._do_action(self._connect)
+    def _pair(self):
         _LOGGER.debug("Sending pair command")
         self._send_request(self.pair_command)
-        _LOGGER.debug("Disconnecting")
-        self._disconnect()
         _LOGGER.debug("Done!")
 
     def create_command(self, command: int) -> bytearray:

tion_btle/tion.py

@@ -463,3 +463,28 @@ def _encode_mode(self, mode: str) -> int:
         :return: integer equivalent of mode
         """
         return self.modes.index(mode) if mode in self.modes else 2
+
+    def pair(self):
+        _LOGGER.debug("Pairing")
+        self._connect()
+        _LOGGER.debug("Connected. BT pairing ...")
+        try:
+            # use private methods to avoid disconnect if already paired
+            self._btle._writeCmd('pair' + '\n')
+            rsp = self._btle._waitResp('mgmt')
+            if rsp['estat'][0] == 0 or rsp['estat'][0] == 19 or rsp['code'][0] == 'success':
+                _LOGGER.debug(rsp['emsg'][0])
+            else:
+                _LOGGER.warning("Unexpected response: %s(%d)", rsp['emsg'][0], rsp['estat'][0])
+                raise TionException(rsp['estat'][0], rsp['emsg'][0])
+            # device-specific pairing
+            _LOGGER.debug("Device-specific pairing ...")
+            self._pair()
+            _LOGGER.debug("Device pair is done")
+        finally:
+            _LOGGER.debug("disconnected")
+            self._disconnect()
+
+    @abc.abstractmethod
+    def _pair(self):
+        """Perform model-specific pair steps"""