Set up project with Spring Boot

[mmerdes]

Basic setup

• Spring Boot version 3.0.4
• Kotlin version 1.8.10
• Gradle version 7.6.1

Quality checks

• code quality with detekt: fail build for long (>17) or complex (cc>4) methods
• code coverage with kover: fail build for low coverage (<80%)

(NB: kover limit set to 0% for now because there is no testable code yet)