Introduce assertions against Cookie attributes in CookieResultMatchers for MockMvc

[sbrannen]

Overview

Servlet API 6.0 introduced jakarta.servlet.http.Cookie.getAttribute(String) for accessing attributes other than the standard attributes such as Max-Age, Secure, etc.

However, there is currently no way to assert the values of such attributes in MockMvc. For example, you cannot assert the value of the SameSite attribute.

In contrast, org.springframework.test.web.reactive.server.CookieAssertions.sameSite(String, String) provides first-class support for asserting against the SameSite attribute when using WebTestClient.

Related Issues

• Support SameSite cookie attribute in MockMvcHttpConnector #30264

Deliverables

• Introduce assertions against Cookie attributes in CookieResultMatchers for MockMvc.
• Consider introducing a dedicated assertion for the SameSite cookie attribute.
• Add DSL support in Kotlin in CookieResultMatchersDsl.kt