Switch from `diesel` to `mysql` #434

Job	Run time
Clippy (cargo clippy)	56s
Integration testing (docker)	1m 47s
Docs (cargo doc)	43s
Format (cargo fmt)	41s
Miri	1m 50s
Check MSRV	2m 12s
security_audit	5s
Outdated	12s
Test on ubuntu-latest (cargo test)	1m 22s
Test on windows-latest (cargo test)	2m 33s
	12m 21s

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