This commit adds a new way to use MockMvc by returning a MvcResult that
is AssertJ compatible. Compared to the existing MockMvc infrastructure,
this new model has the following advantages:
* Can be created from a MockMvc instance
* Dedicated builder methods for easier setup
* Assertions use familiar AssertJ syntax with discoverable assertions
through a DSL
* Improved exception message
See gh-21178
Co-authored-by: Brian Clozel <brian.clozel@broadcom.com>
e7d7cb8641