update app/utils/base64_decoder.py

app/utils/base64_decoder.py

@@ -0,0 +1,18 @@
+import base64
+
+
+class SubscriptionDecoder:
+    @staticmethod
+    def decode(encoded_content: str) -> str:
+        if not encoded_content:
+            return ""
+
+        try:
+            missing_padding = len(encoded_content) % 4
+            if missing_padding:
+                encoded_content += "=" * (4 - missing_padding)
+
+            decoded_bytes = base64.b64decode(encoded_content)
+            return decoded_bytes.decode("utf-8")
+        except Exception as e:
+            raise ValueError(f"Invalid base64 content: {e}")