BTHLABS-61: Service layer refactoring

A journey to fix `ValidationError` in Pocket imports turned service
layer refactoring :D

services/packages/soa/hotpocket_soa/exceptions/frontend.py

@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+from __future__ import annotations
+
+import typing
+
+from .backend import BackendServiceError
+
+
+class SOAError(Exception):
+    def __init__(self, code: int, message: str, *args):
+        super().__init__(code, message, *args)
+        self.code = code
+        self.message = message
+
+        self.data: typing.Any = None
+        if len(args) > 0:
+            self.data = args[0]
+
+    @classmethod
+    def from_backend_error(cls: type[typing.Self], exception: BackendServiceError) -> typing.Self:
+        result = cls(
+            exception.CODE.value,
+            exception.message,
+            exception.data,
+        )
+        result.__cause__ = exception
+
+        return result