SpringBoot Use DynamicPropertySource in MongoDB tests

Hi,

this PR implements @DynamicPropertySource in the MongoDB tests in favor of using custom initializers.

Cheers, Christoph

Comment From: dreis2211

Give me a second to fix the checkstyle warnings.

Comment From: wilkinsona

Thanks, @dreis2211. When merging forwards, I was so pleased at how much simpler the setup for the transactional tests became, I forgot to do the rest of the @DynamicPropertySource changes.

Comment From: wilkinsona

Thanks again, Christoph.