* Implement entity writer context and date time crate enum
* Use entity writer context to render correct rust type according to chrono/time enum
* Add unit test to get col rs type with time crate
* Add date-time-crate flag for cli
* Edit usage of updated get_rs_type method
* Use arg enum for date time crate
* Move date time crate arg enum conversion into commands module
* Directly use arg enum
* Fixing import issues for arg enum w/ help from Billy
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