All date formats now use the class constant for date format
Mockery v1.2.3 introduced a changed to interfaces which was causing our static analysis to fail even though there was no change to functionality. This PR adjusts the interfaces we're using in a non-breaking way.
Problem
Incorrect date format was used as brought up in https://github.com/helpscout/helpscout-api-php/pull/184. This PR applies that fix to both
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Solution