[FEAT]: Cover with tests

[y9vad9]

Description

Not everything for now is covered by tests

Domain layer:

• Cover users domain with tests #46
• Cover timers domain with tests #47
• Cover files domain with tests #48
• Cover authorization domain with tests #49

Data layer:

• Cover users data layer with tests #50
• Cover timers data layer with tests #51
• Cover files data layer with tests #52
• Cover authorization data layer with tests #53