Applied new [ValidateLaCode] attribute to actions and controllers that consume code

[WolfyUK]

Context

AB#254608 AB#260043 #2337

Change proposed in this pull request

• Implemented action filter above for LA codeand applied to controllers/actions
• Updated integration tests to ensure all dummy LA codes are of correct format
• Refactored earlier implementation to instead make use of IValidator

Guidance to review

Dependency on #2337.
Any URL including a bad LA code should fail with 404 and the 'page not found' view. E2E/A11y should be unaffected.

Checklist (add/remove as appropriate)

• Work items have been linked (use AB#)
• Your code builds clean without any errors or warnings
• You have run all unit/integration tests and they pass
• Your branch has been rebased onto main
• You have tested by running locally
• You have reviewed with UX/Design

[jrabbott]

Would -19823 pass this validation as is? Length 6 and is a valid int?

Could use .Must(p=> p.All(char.IsDigit))?

[WolfyUK]

Good spot! Updated

[jrabbott]

What about XXXXXX? Does that pass or fail the validation?

My gut is saying that'll pass based on the 'when'. However I've not used when before so not 100% sure on the behaviour.

[WolfyUK]

One of the other rules fails validation with Organisation identifier must be a number for XXXXXX