Use delegate.get_string to get pin code

bumble/device.py

@@ -2804,23 +2804,13 @@ class Device(CompositeEventEmitter):
 
             async def get_pin_code():
                 pin_code = await connection.abort_on(
-                    'disconnection', pairing_config.delegate.get_number()
+                    'disconnection', pairing_config.delegate.get_string(16)
                 )
 
                 if pin_code is not None:
-                    # TODO: make pin code input more flexible,
+                    pin_code = bytes(pin_code, encoding='utf-8')
-                    # so far only numbers are allowed
-                    pin_code = bytes(str(pin_code), encoding='utf8')
                     pin_code_len = len(pin_code)
-                    if pin_code_len > 16:
+                    assert 0 < pin_code_len <= 16, "pin_code should be 1-16 bytes"
-                        logger.warning(
-                            'pin_code is longer than 16 bytes, truncated to 16'
-                        )
-                        pin_code_len = 16
-                        # the pin_code will be truncated according to pin_code_len
-                        # when converted to byte array in HCI_Object, so we
-                        # are not doing truncation here
-
                     await self.host.send_command(
                         HCI_PIN_Code_Request_Reply_Command(
                             bd_addr=connection.peer_address,
@@ -2829,6 +2819,7 @@ class Device(CompositeEventEmitter):
                         )
                     )
                 else:
+                    logger.debug("delegate.get_string() returned None")
                     await self.host.send_command(
                         HCI_PIN_Code_Request_Negative_Reply_Command(
                             bd_addr=connection.peer_address