fix(contracts_service): Improve datetime handling and add contract metrics

- Import timezone from datetime module for UTC timestamp generation
- Import MetricUnit from aws_lambda_powertools.metrics for proper metric typing
- Replace strftime formatting with isoformat() for ISO 8601 compliant timestamps in create_contract and update_contract functions
- Add metric tracking for successful contract creation events
- Rename UpdateExpression attribute from modified_date to contract_last_modified_on for consistency
- Ensures timestamps are timezone-aware and use UTC for consistency across distributed systems

Author: sliedig

unicorn_contracts/src/contracts_service/contract_event_handler.py

@@ -3,14 +3,14 @@
 
 import os
 import uuid
-from datetime import datetime
+from datetime import datetime, timezone
 
 import boto3
 from boto3.dynamodb.conditions import Attr
 from botocore.exceptions import ClientError
 
 from aws_lambda_powertools.logging import Logger
-from aws_lambda_powertools.metrics import Metrics
+from aws_lambda_powertools.metrics import Metrics, MetricUnit
 from aws_lambda_powertools.tracing import Tracer
 from aws_lambda_powertools.utilities.data_classes import event_source, SQSEvent
 from aws_lambda_powertools.utilities.typing import LambdaContext
@@ -76,7 +76,7 @@ def create_contract(event: dict) -> None:
         DynamoDB put Item response
     """
 
-    current_date = datetime.now().strftime("%d/%m/%Y %H:%M:%S")
+    current_date = datetime.now(timezone.utc).isoformat()
     contract = {
         "property_id": event["property_id"],  # PK
         "address": event["address"],
@@ -105,6 +105,7 @@ def create_contract(event: dict) -> None:
 
         # Annotate trace with contract status
         tracer.put_annotation(key="ContractStatus", value=contract["contract_status"])
+        metrics.add_metric(name="ContractCreated", unit=MetricUnit.Count, value=1)
 
     except ClientError as e:
         code = e.response["Error"]["Code"]
@@ -147,13 +148,13 @@ def update_contract(contract: dict) -> None:
 
     try:
         contract["contract_status"] = ContractStatus.APPROVED.name
-        current_date = datetime.now().strftime("%d/%m/%Y %H:%M:%S")
+        current_date = datetime.now(timezone.utc).isoformat()
 
         response = table.update_item(
             Key={
                 "property_id": contract["property_id"],
             },
-            UpdateExpression="set contract_status=:t, modified_date=:m",
+            UpdateExpression="set contract_status=:t, contract_last_modified_on=:m",
             ConditionExpression=Attr("property_id").exists()
             & Attr("contract_status").is_in([ContractStatus.DRAFT.name]),
             ExpressionAttributeValues={