model: refactor the fix for Edm.DateTimeOffset.from_json()

Use solution provided in issue #202 by @squeakyboots (#233)

Author: phanak-sap

pyodata/v2/model.py

@@ -530,15 +530,16 @@ def to_json(self, value):
 
     def from_json(self, value):
         # special edge case:
-        # datetimeoffset'yyyy-mm-ddThh:mm[:ss]' = defaults to UTC, when offset value is not provided in responde data by service but the metadata is EdmDateTimeOffset
+        # datetimeoffset'yyyy-mm-ddThh:mm[:ss]' = defaults to UTC, when offset value is not provided in response
+        #   by service, but the metadata is EdmDateTimeOffset
         # intentionally just for from_json, generation of to_json should always provide timezone info
-        if re.match(r"^/Date\((?P<milliseconds_since_epoch>-?\d+)\)/$", value):
-            value = value.replace(')', '+0000)')
-
-        matches = re.match(r"^/Date\((?P<milliseconds_since_epoch>-?\d+)(?P<offset_in_minutes>[+-]\d+)\)/$", value)
+        matches = re.match(r"^/Date\((?P<milliseconds_since_epoch>-?\d+)(?P<offset_in_minutes>[+-]\d+)?\)/$", value)
         try:
             milliseconds_since_epoch = matches.group('milliseconds_since_epoch')
-            offset_in_minutes = int(matches.group('offset_in_minutes'))
+            if matches.group('offset_in_minutes') is not None:
+                offset_in_minutes = int(matches.group('offset_in_minutes'))
+            else:
+                offset_in_minutes = 0
         except (ValueError, AttributeError):
             raise PyODataModelError(
                 f"Malformed value {value} for primitive Edm.DateTimeOffset type."