🚧Remove Assert Extensions

[CalvinWilkinson]

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• I have updated the title without removing the 🚧 emoji.

Description

Replace all AssertExtensions uses across the code base and then delete the AssertExtensions file.

Reason:
Over many months, all of the assertion code across the codebase has been getting refactored to use the FluentAssertions library API. This has greatly improved the assertion code which has made the extension methods provided by the AssertExtensions class not required anymore.

Note
Most of the uses of the extensions methods will probably be replaced just by completing the rest
of the issues for refactoring assertion code. These issues are listed in the list of issue dependencies below.
Please complete the issue dependencies below first before starting this issue.

Acceptance Criteria

• All uses of the AssertExtensions extensions methods replaced with FluentAssertion or standard XUnit code
• The AssertExtensions file has been deleted from the code base.

ToDo Items

• Change type labels added to this issue. Refer to the Change Type Labels section below.
• Priority label added to this issue. Refer to the Priority Type Labels section below.
• Issue linked to the correct milestone (if applicable).

Issue Dependencies

• 🚧Refactor unit test assertions #105
• 🚧Refactor unit test assertions #106
• 🚧Refactor unit test assertions #107

Related Work

No response

Additional Information:

Change Type Labels

Change Type	Label
Bug Fixes	🐛bug
Breaking Changes	🧨breaking changes
New Feature	✨new feature
CICD Changes	♻️cicd
Config Changes	⚙️config
Performance Improvements	🏎️performance
Code Doc Changes	🗒️documentation/code
Product Doc Changes	📝documentation/product

Priority Type Labels

Priority Type	Label
Low Priority	low priority
Medium Priority	medium priority
High Priority	high priority

Code of Conduct

• I agree to follow this project's Code of Conduct.

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