Time columns don't include milliseconds

[jwoertink]

When we set the created_at and updated_at fields, we just called created_at.value = Time.utc. That value in the DB looks like 2021-09-10 18:08:39+00, but if you actually inspect Time.utc you'll get something that looks like 2021-09-10 18:03:38.655286917 UTC. Storing the milliseconds makes a HUGE difference when you're sorting by created_at in your specs especially if you're doing any window function using created_at.

We need to figure out how to include milliseconds on these fields by default.

Related: #393 if we just let SQL handle it via NOW(), it would be fine.

EDIT: turns out it's all Time columns, not just created_at and updated_at.

[jwoertink]

This happens here:

avram/src/avram/charms/time_extensions.cr

Lines 74 to 76 in a3d830c

	def to_db(value : Time)
	value.to_s
	end

Time.utc.to_s              #=> "2021-09-10 19:21:22 UTC"
Time.utc.to_s("%F %X.%6N") #=> "2021-09-10 19:21:22.872793"

We account for time formats when pulling the value out of the DB, but not for inserting the value.