Use timezone aware datetimes instead of timezone naive datetimes:
- Update mongodb client to use tz-aware conversion
- Convert dt_now() to return timezone aware UTC date
- Rename to_k8s_date -> date_to_str, just returns ISO UTC date with 'Z'
(instead of '+00:00' suffix)
- Rename from_k8s_date -> str_to_date, returns timezone aware date from
str
- Standardize all string<->date conversion to use either date_to_str or
str_to_date
- Update frontend to assume iso date, not append 'Z' directly
- Update tests to check for 'Z' suffix on some dates
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Co-authored-by: Ilya Kreymer <ikreymer@gmail.com>
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