cli: better Extract method

CHANGELOG.md

+# 1.1.2
+
+- Extract a API method to authenticate from python
 # 1.1.1
 
 - Introduce `grid5000-auth` to facilitate the creation of credential file

grid5000/__version__.py

-__version__ = "1.1.1"
+__version__ = "1.1.2"

grid5000/cli.py

@@ -48,6 +48,7 @@ def auth(user: str):
     password = getpass("Grid'5000 password: ")
     path.write_text("\n".join([f"username: {user}", f"password: {password}"]))
     print(f"{CONF_PATH} created successfully")
+    path.chmod(0o600)
 
 
 def cli_auth():