TS-1416: Change to EndOfTenureDate validation so it can be on the StartOfTenureDate

[martapederiva]

Link to JIRA ticket

https://hackney.atlassian.net/browse/TS-1416

Describe this PR

What is the problem we're trying to solve

The BTA tool needs to be able to end a booking on the same day it starts. After convos with Housing and Finance (see ticket) we are now proceeding with such changes.

What changes have we introduced

Changes to validation + test
Also minor refactoring of surrounding tests as date setting was not super solid

Follow up actions after merging PR

Updating package version in consuming API + listener (for coherence)

[Duslerke]

The PR changes in here are fine, but I think I've missed what's not in this PR.

This could be an issue:

tenure-shared/Hackney.Shared.Tenure/Boundary/Requests/Validation/TenureInformationValidatorWhenOnlyStartDate.cs

Lines 13 to 18 in 61af120

	When(tenure => tenure.EndOfTenureDate != null, () =>
	{
	RuleFor(x => x.StartOfTenureDate)
	.LessThan(x => x.EndOfTenureDate)
	.WithErrorCode(ErrorCodes.TenureEndDate);
	});

[Duslerke]

Seems like it will be alright.

The effect of this is relaxed restriction on start/end date validation, which shouldn't break any API functionality contract-wise.

[Duslerke]

Of course, some tests on the Tenure API will need to be updated as well to match this new behaviour.
Tests like:
https://github.com/LBHackney-IT/tenure-api/blob/43446370f9307fc93159324daf0cea19a4b1e673/TenureInformationApi.Tests/V1/Controllers/TenureInformationControllerTests.cs#L311

[Duslerke]

The change in error code is fine. Just a string change.