copy workaround from ahbicht

https://github.com/Hochfrequenz/ahbicht/blob/ac44e80b76d3a952ce14fb89b82e7b43e574876c/src/ahbicht/__init__.py#L17

src/edi_energy_scraper/epoch.py

@@ -2,7 +2,25 @@
 this module contains the epoch enum
 """
 
-from enum import StrEnum
+import sys
+
+if sys.version_info.major == 3 and sys.version_info.minor >= 11:
+    from enum import StrEnum
+
+    # We have to use the builtin / std lib enum.StrEnum in Python >= 3.11, because the behaviour of (str,Enum) changed:
+    # class Foo(str, Enum):
+    #     MEMBER = "MEMBER"
+    # f"{a_str_enum_member}" results in "MEMBER" for Python < v3.11 but "Foo.MEMBER" in Python >= v3.11
+else:
+    from enum import Enum
+
+    class StrEnum(str, Enum):  # type:ignore[no-redef]
+        """
+        An enum class of which each member has a string representation.
+        This is a workaround for Python <v3.11 because enum.StrEnum was introduced in Python 3.11.
+        """
+
+        # We'll live with this class for Python <v3.11. The unit test for python 3.9-3.11 ensure that this works.
 
 
 class Epoch(StrEnum):  # pylint: disable=too-few-public-methods