[CodeQuality] Fix Sonarqube reported issues

[daltonfury42]

We have enabled Sonarqube, it has reported some bugs and code smells. Most of these are trivial.

Report: https://sonarcloud.io/dashboard?id=SimplQ_simplQ-backend

[daltonfury42]

All issues have been fixed. We have a integration test here, we need to configure it to come in coverage report