fix(core): Typing in config + utils (#692)

Supports:
#305
Related : #691 

```bash
poetry run mypy --config-file pyproject.toml core/testcontainers/core/config.py core/testcontainers/core/utils.py
Success: no issues found in 2 source files
```

core/testcontainers/core/config.py

@@ -30,7 +30,7 @@ def read_tc_properties() -> dict[str, str]:
     tc_files = [item for item in [TC_GLOBAL] if exists(item)]
     if not tc_files:
         return {}
-    settings = {}
+    settings: dict[str, str] = {}
 
     for file in tc_files:
         with open(file) as contents:
@@ -60,14 +60,14 @@ class TestcontainersConfiguration:
     """
 
     @property
-    def docker_auth_config(self):
+    def docker_auth_config(self) -> Optional[str]:
         config = self._docker_auth_config
         if config and "DOCKER_AUTH_CONFIG" in _WARNINGS:
             warning(_WARNINGS.pop("DOCKER_AUTH_CONFIG"))
         return config
 
     @docker_auth_config.setter
-    def docker_auth_config(self, value: str):
+    def docker_auth_config(self, value: str) -> None:
         if "DOCKER_AUTH_CONFIG" in _WARNINGS:
             warning(_WARNINGS.pop("DOCKER_AUTH_CONFIG"))
         self._docker_auth_config = value
@@ -76,7 +76,7 @@ def tc_properties_get_tc_host(self) -> Union[str, None]:
         return self.tc_properties.get("tc.host")
 
     @property
-    def timeout(self):
+    def timeout(self) -> int:
         return self.max_tries * self.sleep_time
 
 

core/testcontainers/core/utils.py

@@ -3,6 +3,7 @@
 import platform
 import subprocess
 import sys
+from typing import Any, Optional
 
 LINUX = "linux"
 MAC = "mac"
@@ -18,14 +19,15 @@ def setup_logger(name: str) -> logging.Logger:
     return logger
 
 
-def os_name() -> str:
+def os_name() -> Optional[str]:
     pl = sys.platform
     if pl == "linux" or pl == "linux2":
         return LINUX
     elif pl == "darwin":
         return MAC
     elif pl == "win32":
         return WIN
+    return None
 
 
 def is_mac() -> bool:
@@ -53,7 +55,7 @@ def inside_container() -> bool:
     return os.path.exists("/.dockerenv")
 
 
-def default_gateway_ip() -> str:
+def default_gateway_ip() -> Optional[str]:
     """
     Returns gateway IP address of the host that testcontainer process is
     running on
@@ -66,11 +68,12 @@ def default_gateway_ip() -> str:
         ip_address = process.communicate()[0]
         if ip_address and process.returncode == 0:
             return ip_address.decode("utf-8").strip().strip("\n")
+        return None
     except subprocess.SubprocessError:
         return None
 
 
-def raise_for_deprecated_parameter(kwargs: dict, name: str, replacement: str) -> dict:
+def raise_for_deprecated_parameter(kwargs: dict[Any, Any], name: str, replacement: str) -> dict[Any, Any]:
     """
     Raise an error if a dictionary of keyword arguments contains a key and suggest the replacement.
     """