Fix (?) timezone issue for datetime

[jdeniau]

objects from datetime and date columns are returned as Date objects, but Date objects is just bad.

The mariadb timezone can be specified on the system and mysql library can pass a timezone as connection option, but let's keep it simple for now :

As Date are construct with "local" timezone, imagine the following date:

d = new Date('2020-01-01 00:00:00')
// Date Wed Jan 01 2020 00:00:00 GMT+0100 (heure normale d’Europe centrale)

Formating this with .toISOString() will give us "2019-12-31T23:00:00.000Z" (ISO string is UTC+0 for JS), but we do want only the local value.

We do implement a small date utility function to format the date that use the "Y-m-d H:i:s" format.

In the future, we might want to use another library, like temporal, luxon or dare-fns, but for the moment the helper works fine 👌