Date::fromDbStringLocal() fails if time is missing

[Baxulio]

Description

The function trantor::Date::fromDbStringLocal() expects a full timestamp string in the format: "YYYY-MM-DD HH:MM:SS[.ffffff]", but if you pass only a date string like "1970-01-01", it fails silently and returns an invalid Date object, which can lead to confusing behavior.

Example

std::string s = trantor::Date().toDbStringLocal();  // "1970-01-01"
auto d = trantor::Date::fromDbStringLocal(s);
LOG_DEBUG << d.toDbStringLocal();  // Outputs: 1899-00--1

Expected Behavior

The parser should either support "YYYY-MM-DD" as a valid input by assuming zero time

[FujiwaraNaoto]

I'm new to this community. I'd like to make a pull request to resolve this issue.