It is rather tricky to cleanup a test in Rust, luckily I found the
`Drop` pattern where a random struct is created at the beginning of the
test and `Drop` is implemented for this struct where all the cleanup
happens in this implementation. Works like a charm.

Otherwise the record can't be used anymore after calling its insert
method.

This will show when you can leave work after 8 hours of presence.

A temporary timestamp of type work is appended to the records so the
duration until now is shown and not that one between the first and last
database record.
This also converts the timestamp to UTC when selecting it from the
database, otherwise the database records would have an offset depending
on the local timezone¹.

¹ this screams for a test

The intended use of this tool is to track how long I am at work.
Besides, it was a really nice exercise in doing Rust.