Use actual and expected in the order that is expected by AssertJ

[floscher]

This mainly corrects the error messages in case of test failures, where currently the actual value is showing as the expected value and vice versa.

assertThat() takes the actual value as parameter instead of the expected value, see https://www.javadoc.io/doc/org.assertj/assertj-core/latest/org/assertj/core/api/Assertions.html#assertThat(boolean)

Currently it looks like this, when for example the conversion from entity to dto and back is broken and a field is not the expected "expectedValue", but null instead:

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