TelegramClient.send_code_request(): Change logic of methods invocation

Before:
  First call, force_sms=False: SendCodeRequest
  Next call, force_sms=False: SendCodeRequest
  First call, force_sms=True: raise ValueError
  Next call, force_sms=True: ResendCodeRequest

That's inconvenient because the user must remember whether the code requested at all and whether the request was successful.
In addition, the repeated invocation of SendCodeRequest does nothing.

This commit changes logic to this:
  First call, force_sms=False: SendCodeRequest
  Next call, force_sms=False: ResendCodeRequest
  First call, force_sms=True: SendCodeRequest, ResendCodeRequest
  Next call, force_sms=True: ResendCodeRequest

telethon/telegram_client.py

@@ -138,23 +138,24 @@ class TelegramClient(TelegramBareClient):
         :param str | int phone:
             The phone to which the code will be sent.
         :param bool force_sms:
-            Whether to force sending as SMS. You should call it at least
-            once before without this set to True first.
+            Whether to force sending as SMS.
         :return auth.SentCode:
             Information about the result of the request.
         """
         phone = EntityDatabase.parse_phone(phone) or self._phone
-        if force_sms:
-            if not self._phone_code_hash:
-                raise ValueError(
-                    'You must call this method without force_sms at least once.'
-                )
-            result = self(ResendCodeRequest(phone, self._phone_code_hash))
-        else:
+
+        if not self._phone_code_hash:
             result = self(SendCodeRequest(phone, self.api_id, self.api_hash))
             self._phone_code_hash = result.phone_code_hash
+        else:
+            force_sms = True
 
         self._phone = phone
+
+        if force_sms:
+            result = self(ResendCodeRequest(phone, self._phone_code_hash))
+            self._phone_code_hash = result.phone_code_hash
+
         return result
 
     def sign_in(self, phone=None, code=None,