Fix warnings and small cleanup

[urielsalis]

Changelist

• Fix Intellij warnings.
• Rename module to comply with Java recommendations
• Remove unnecessary annotations as they are already included with @SpringBootApplication
• Use constructor injection instead of field injection following Spring recommendations
• Use .isEmpty() instead of relying on exceptions to know if a parameter was passed, similar to other modules

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation (adds or revises project documentation)

Local configuration:

• OS: Windows
• JDK: OpenJDK 11

[zocat64]

I've considered taking action regarding the module name warning in the past, but ultimately decided to keep it for stylistic reasons. Everything else looks fine.

[urielsalis]

Sounds good, feel free to merge

[zocat64]

I will sometime this weekend. I've got 4 PRs to deal with and not a lot of time on my hands, unfortunately.

[zocat64]

Merged in #34.