Remove deprecated reminder endpoint (#66)

Implement deadlines (#60)

* Implement deadlines

* Fix build

Update Todoist.Net project and package versions

The Todoist.Net version has been updated from 7.0.0 to 8.0.0. Additionally, the System.Text.Json package version has been incremented from 8.0.3 to 8.0.4, and the xunit version in the Todoist.Net.Tests project has been upgraded from 2.8.1 to 2.9.0.

Update project version and dependencies

The project version has been incremented to 7.0.0, and now includes Ahmed Zaki as an author. The version of the dotnet-sonarscanner dependency has also been updated. Additionally, the versions of testing dependencies in Todoist.Net.Tests have been updated.

Update Todoist.Net version to 6.1.0

The version prefix for the Todoist.Net project has been updated. This change moves the version from 6.0.0 to 6.1.0.

Reopen "Fix DueDate.StringDate conversion to and from DateTime." (#41)

* Added FakeLocalTimeZone helper class.
The class is used to change the time zone of the tests upon initialization, and resets it back when disposed.

* Added more tests for DueDate model.
The added tests ensure consistency in StringDate property setter and getter.

* Changed date formatting in DueDate.StringDate property.
Date is now converted using the round-trip format without milliseconds.
Date is also no longer being converted to universal time before formatting.

* Made a simple change in floating due date test.
DateTimeKind is switched to Unspecified instead of Utc since the due date should be treated as floating.

* Fixed date convertion in `DueDate.StringDate` getter.
The fix reverts back to depending on `DueDate.Timezone` property to determine the conversion formatting.
However, it doesn't convert the `DueDate.Date` value to universal time unless the `DueDate` is intended to be fixed.

* Made a simple fix to the "fixed timezone" `DueDate` test.
Timezone info was missing for a fixed date.

* Fixed CreateNewItem_DueDateIsLocal_DueDateNotChanged test.
Since floating due dates are now converted to `Unspecified` date time, the method `ToLocalTime` is no longer used because it assumes the given date as `UTC`.

* Replaced DueDate public constructors with static methods.
Methods include detailed documentation comments.

* Removed redundant checks in DueDate.StringDate getter.
Static methods that are used to instantiate DueDates are now in charge of handling different kinds of dates.

* Updated tests with new DueDate static methods.

* Remove randomization in tests.
Fake time zone random selection is replaced by pre-determined custom offset.

* Remove unnecessary comments.

* Removed unnecessary SuppressFinalize call in DueDateTests.

Fix due date parsing (#32)

Update package version

Fix move item bug introduced in the previous commit

Renaming CompletedDate on CompletedItem for v9 migration (#18)