feat: add posibility to use token file in hetzner config

example-config.yaml

@@ -7,7 +7,10 @@ server:
 upstream:
   provider: hetzner
   hetzner:
-    api_token: "YOUR_HETZNER_API_TOKEN"
+    # Provide the API token directly
+    # api_token: "YOUR_HETZNER_API_TOKEN"
+    # OR provide the path to a file containing the token
+    api_token_file: "/path/to/your/hetzner_token.txt"
 clients:
   client1:
     secret: "s3cr3t123"