fix: DateTime incorrectly encoded when microsecond precision > # digits

[vlymar]

@ruslandoga, I found this bug while investigating these errors in my application:

** (Ch.Error) Code: 457. DB::Exception: Value 1716753646. 99856 cannot be parsed as DateTime64 for query parameter '$6' because it isn't parsed completely: only 11 of 17 bytes was parsed: 1716753646. (BAD_QUERY_PARAMETER) (version 23.11.5.29 (official build))

I found a bug in our logic for encoding microsecond values. We left pad the value, but with the default space parameter rather than a 0 😅. See the failing test in the first commit for the repro.

iex(23)> d
~U[2024-05-26 20:00:46.099856Z]
iex(24)> d.microsecond
{99856, 6}

[vlymar]

my formatter did this, lemme know if you'd rather this line not be touched

[ruslandoga]

Thank you!

[ruslandoga]

I published the fix as v0.2.6: https://hex.pm/packages/ch