Add unit tests

What does this MR do?

• Adds unit tests for :
  • jwt.go
  • reporter.go
  • trivy.go
  • validator.go
• Extracts mocks which are required for unit tests
• Refactor code to do dependency injection

Why are we doing this?

In order to properly test our code

What are the relevant issue numbers?

Add Unit tests for Trivy K8S wrapper (gitlab-org/gitlab#432798 - closed)