Migrate from deprecated assertThat() to org.hamcrest.MatcherAssert.assertThat()

The org.junit.Assert that our unit tests all extend from indicates that assertThat() is deprecated, and to use org.hamcrest.MatcherAssert.assertThat() instead.

We currently in our tests have both a mix of the assertThat() AND MatcherAssert.assertThat() methods...

It appears that I can also just override the assertThat() method defined in org.junit.Assert in our base test classes to be one that calls out MatcherAssert.assertThat() which might let us change fewer lines of code..

I'd love some direction from more experienced folks on what the right direction to go is!