refactor(server): set an appropriate default timestamp precision for datetime/timestamp DB columns

[fabis94]

Re: #962 Currently blocked by a Knex issue/PR that would enable us to do this in the first place:

Issue: https://github.com/knex/knex/issues/5308 PR: https://github.com/knex/knex/pull/5311

After the knex feature is launched, we just need to set a new config option for knex and that's that.