Add a date formatter for new public API test cases

[amoghrajesh]

Body

As per this comment: #43874 (comment), we need to add a date formatter in our new API test cases. This is because right now, we do something like this: "data_interval_end": dr.data_interval_end.isoformat().replace("+00:00", "Z") to account for the move from +00:00 to Z time format.

Adding this new formatter will clean up the tests and make it easier to extend.

Committer

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