Migrate MockMvc Hamcrest assertions to AssertJ - #1120

What's changed?

Adds a Spring Framework 6.2 migration recipe that converts chained MockMvc andExpect(...) assertions to the AssertJ-based MockMvc API.

The recipe wraps existing MockMvc.perform(...) calls with MockMvcTester and converts each expectation to matches(...), preserving the original request builders and result matchers.

What's your motivation?

• Closes Migrate MockMvc Hamcrest assertions over to AssertJ #697.

Spring Framework 6.2 introduced AssertJ support for MockMvc. This recipe provides a safe migration path for existing Hamcrest-style assertion chains and is included in the Spring Framework 6.2 upgrade recipe.

Anything in particular you'd like reviewers to focus on?

The migration deliberately preserves existing request builders and ResultMatcher instances through MockMvcTester.perform(...).matches(...).

Have you considered any alternatives or workarounds?

A fuller conversion to fluent request construction and specialized AssertJ assertions would require mapping many request-builder and matcher variants. This first migration uses Spring's documented AssertJ bridge to preserve behavior safely.

andExpectAll(...) is intentionally left unchanged because its aggregate-failure semantics cannot be preserved by a chain of AssertJ assertions.

Any additional context

The recipe includes positive coverage for chained andExpect(...) calls and negative coverage for andExpectAll(...).

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files