refactor: use Auto<T> for id in DatabaseUser

[m4tx]

This was missed when Auto structure was added to the project.

[codecov]

Codecov Report

Attention: Patch coverage is 80.95238% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cot/src/db.rs	50.00%	4 Missing ⚠️

Flag	Coverage Δ
rust	86.00% <80.95%> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
cot/src/auth/db.rs	78.18% <100.00%> (+1.51%)	⬆️
cot/src/db.rs	90.84% <50.00%> (-0.73%)	⬇️