Make all None by default arguments accept None value (#450)

Signed-off-by: Paweł Szczur <[email protected]>

Author: orian

clickhouse_connect/driver/httputil.py

@@ -55,10 +55,10 @@ def close_managers():
 def get_pool_manager_options(keep_interval: int = DEFAULT_KEEP_INTERVAL,
                              keep_count: int = DEFAULT_KEEP_COUNT,
                              keep_idle: int = DEFAULT_KEEP_IDLE,
-                             ca_cert: str = None,
+                             ca_cert: Optional[str] = None,
                              verify: bool = True,
-                             client_cert: str = None,
-                             client_cert_key: str = None,
+                             client_cert: Optional[str] = None,
+                             client_cert_key: Optional[str] = None,
                              **options) -> Dict[str, Any]:
     socket_options = core_socket_options.copy()
     if getattr(socket, 'TCP_KEEPINTVL', None) is not None:
@@ -88,12 +88,12 @@ def get_pool_manager_options(keep_interval: int = DEFAULT_KEEP_INTERVAL,
 def get_pool_manager(keep_interval: int = DEFAULT_KEEP_INTERVAL,
                      keep_count: int = DEFAULT_KEEP_COUNT,
                      keep_idle: int = DEFAULT_KEEP_IDLE,
-                     ca_cert: str = None,
+                     ca_cert: Optional[str] = None,
                      verify: bool = True,
-                     client_cert: str = None,
-                     client_cert_key: str = None,
-                     http_proxy: str = None,
-                     https_proxy: str = None,
+                     client_cert: Optional[str] = None,
+                     client_cert_key: Optional[str] = None,
+                     http_proxy: Optional[str] = None,
+                     https_proxy: Optional[str] = None,
                      **options):
     options = get_pool_manager_options(keep_interval,
                                        keep_count,