DEPR: casting in DatetimeLikeArrayMixin.isin

[jbrockmendel]

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Reproducible Example

NA

Issue Description

DatetimeLikeArrayMixin.isin casts pretty aggressively. In particular I think we shouldn't be parsing strings here. We should deprecate and tell users to cast explicitly.

Expected Behavior

NA

Installed Versions

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[topper-123]

So just to be clear, it's allowed to do e.g. dt_arr.isin(['2018-01-01', '2018-01-02']) and we should deprecate this and make the users convert to first, e.g. dt_arr.isin(pd.array(['2018-01-01', '2018-01-02'], dtype=" datetime64[ns]"))?

+1 from me to that.

[jbrockmendel]

Yes that is what I have in mind.