Fix all the compilation warning in the cloud agent project

[yshyn-iohk]

Proposed feature

Having warnings impacts the code quality.
Fixing all warnings in one PR is difficult, so any PR that reduces the warning should be linked to this issue.
After the riching 0-warning stage, it's important to harden the sbt setting to treat warnings as errors and not allow the introduction of the warning in the codebase.

Feature description

Having 0 warnings proves the high level of code quality

Anything else?

No response

[FabioPinheiro]

My PR totally or at least partially fix this #1251