fix: Remove DateTime in favour of TimeProvider and DateTimeOffset

[pm7y]

No description provided.

[Copilot]

Pull request overview

This pull request replaces DateTime with DateTimeOffset and introduces TimeProvider for improved testability and better handling of timezone-aware timestamps throughout the application. The changes align with modern .NET best practices for time handling.

Key changes:

• Introduces TimeProvider as a singleton service registered in DI for controllable time in tests
• Converts RetryScheduler from a static class to an instance class with TimeProvider dependency
• Updates all time-dependent entities and services to use DateTimeOffset instead of DateTime
• Adds FakeTimeProvider test helper for deterministic time-based testing
• Improves validation logic for timezone handling in EventGridEvent and CloudEvent entities
• Updates Topic handling in EventGridEvent to use internal SetTopic() method for clearer intent

Reviewed changes

Copilot reviewed 39 out of 39 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
Program.cs	Registers TimeProvider.System and RetryScheduler as singletons in DI container
SubscriptionSettings.cs	Converts validation expiry tracking from DateTime to DateTimeOffset, changes ValidationPeriodExpired to method accepting current time
HttpSubscriberSettings.cs	Mirrors SubscriptionSettings changes for HTTP subscriber validation
SasKeyValidator.cs	Adds TimeProvider dependency and uses it for token expiry validation with CultureInfo.InvariantCulture
RetryScheduler.cs	Converts from static class to instance class with TimeProvider dependency for testable retry scheduling
RetryDeliveryBackgroundService.cs	Injects TimeProvider and RetryScheduler, uses timeProvider.GetUtcNow() throughout for consistent time handling
InMemoryDeliveryQueue.cs	Adds TimeProvider dependency for determining due deliveries
EventGridSchemaFormatter.cs	Adds TimeProvider dependency for setting EventTime when converting CloudEvents
DeliveryPropertyResolver.cs	Updates DateTime parsing to DateTimeOffset with InvariantCulture
PendingDelivery.cs	Changes EnqueuedTime and NextAttemptTime to DateTimeOffset, converts IsExpired to method accepting current time
EventGridEvent.cs	Updates time validation to use DateTimeOffset, improves timezone detection, adds SetTopic() method with tracking
DeliveryAttempt.cs	Changes AttemptTime from DateTime to DateTimeOffset
DeadLetterEvent.cs	Changes PublishTime and LastDeliveryAttemptTime to DateTimeOffset
CloudEvent.cs	Updates time validation to use DateTimeOffset with improved timezone handling
ValidateSubscriptionCommandHandler.cs	Injects TimeProvider for validation period checking
ValidateAllSubscriptionsCommandHandler.cs	Injects TimeProvider and uses it for generating validation event timestamps
SendNotificationEventsToSubscriberCommandHandler.cs	Updates to use SetTopic() method instead of direct property assignment
Test files	Updates all test files to use TimeProvider.System or FakeTimeProvider for deterministic testing
FakeTimeProvider.cs	New test helper providing controllable time for testing with Advance() and SetUtcNow() methods
.editorconfig	Increases severity of primary constructor preference from suggestion to warning for consistency

[Copilot]

Extra space before the closing angle bracket in the parameter documentation.

Suggested change

	/// <param name="now" >
	/// <param name="now">

[Copilot]

Consider using expiry.ToString("o") directly instead of converting to UtcDateTime first. Since expiry is already a DateTimeOffset, the ToString("o") format specifier will produce the ISO 8601 format with timezone information. The intermediate conversion to UtcDateTime is unnecessary.

Suggested change

	var decodedExpiration = expiry.UtcDateTime.ToString("o");
	var decodedExpiration = expiry.ToString("o");

[Copilot]

The default value DateTimeOffset.UtcNow bypasses the TimeProvider abstraction introduced in this PR. While this works as a fallback, it reduces testability since tests cannot control this timestamp. Consider either removing the default value and making this property required, or ensuring callers always explicitly set this value (as tests already do). For consistency with the TimeProvider pattern, the SendNotificationEventsToSubscriberCommandHandler should set these values explicitly using TimeProvider.

[Copilot]

The default value DateTimeOffset.UtcNow bypasses the TimeProvider abstraction. However, in production code (RetryDeliveryBackgroundService line 134), this value is always explicitly set using timeProvider.GetUtcNow(), so the default is never actually used. Consider removing this default value to make the intent clearer and prevent accidental use of the uncontrolled timestamp.

Suggested change

	public DateTimeOffset AttemptTime { get; init; } = DateTimeOffset.UtcNow;
	public DateTimeOffset AttemptTime { get; init; }

[Copilot]

Extra space before the closing angle bracket in the parameter documentation.

[Copilot]

The _createdAt field uses DateTimeOffset.UtcNow directly in the field initializer, bypassing the TimeProvider abstraction that was introduced in this PR. This makes the code untestable since tests cannot control this timestamp. Consider initializing this value through a constructor parameter or passing the creation time when ValidationPeriodExpired is called, similar to how it's done in PendingDelivery.IsExpired.

[Copilot]

Extra space before the closing angle bracket in the parameter documentation.

[Copilot]

The _createdAt field uses DateTimeOffset.UtcNow directly in the field initializer, bypassing the TimeProvider abstraction that was introduced in this PR. This makes the code untestable since tests cannot control this timestamp. Consider initializing this value through a constructor parameter or passing the creation time when ValidationPeriodExpired is called, similar to how it's done in PendingDelivery.IsExpired.