Fix encode_param for DateTime

[iStefo]

I noticed that DateTime params close to epoch weren't encoded correctly, resulting in a query error. The reason is this bug report, which won't be fixed: ClickHouse/ClickHouse#64708

As a workaround, I pad the encoded seconds with leading zeros, taking special care to not break in the case of negative values.

This actually lead to the discovery of another bug, ClickHouse/ClickHouse#96745. We can wait for initial feedback on that one before we commit (and either fixate the unexpected behavior in the test or not).

I noticed that NaiveDataTime always uses ISO 8601 format, is there a specific reason for this or should we unify the encoding of both data types?

[ruslandoga]

👋 @iStefo

Thank you!

I noticed that NaiveDataTime always uses ISO 8601 format, is there a specific reason for this or should we unify the encoding of both data types?

ClickHouse treats "text" timestamps as local instead of UTC and converts them to either the server's timezone or the column definition's timezone, which felt like a correct default behaviour for NaiveDataTime.