Analogous to the attributeDoesNotExist() method in ModelResultMatchers, this commit introduces a new sessionAttributeDoesNotExist() method in RequestResultMatchers which asserts that the given attributes are null in the HttpSession. Closes gh-23756
Analogous to the attributeDoesNotExist() method in ModelResultMatchers, this commit introduces a new sessionAttributeDoesNotExist() method in RequestResultMatchers which asserts that the given attributes are null in the HttpSession. Closes gh-23756