Use typed assertions for RestActions

[MinnDevelopment]

Pull Request Etiquette

• [ ] I have checked the PRs for upcoming features/bug fixes.
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Changes

• [ ] Internal code
• [ ] Library interface (affecting end-user code)
• [ ] Documentation
• [x] Other: Testing

Closes Issue: NaN

Description

Further improve testing framework using RestActionAssertions, similar to assertThat.