[issues-100] - Fix the Spotless Maven plugin configuration

[fabiobrz]

Description

Resolves #100

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change
• Chore (non-breaking change which doesn't affect codebase;
  test, version modification, documentation, etc.)

Checklist

• Code contributed by me aligns with current project license: Apache 2.0
• Pull Request contains a description of the changes
• Pull Request does not include fixes for multiple issues/topics
• Code is self-descriptive and/or documented
• I have implemented unit tests to cover my changes
• N/A I tested my code in OpenShift - just code formatting configuration

[fabiobrz]

Thinking a bit more about this, the reason for skipping the applications sources is that actually there can be cases where them might carry license headers as well.
We need some kind of mechanism to prevent Spotless from adding the license header to such files.