Boyscouting (#558)

* Boyscouting: Docker conventions

* Boyscouting: JUnit 5 conventions ("It is generally recommended to omit the public modifier for test classes, test methods, and lifecycle methods unless there is a technical reason for doing so)"

* Boyscouting: typo in RepositoryValidationInterceptorFactoryDstu3

* Boyscouting: use List.of instead of Guava; use StandardCharsets instead of Guava; remove unused imports

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Co-authored-by: Gerlach, Winfried <Winfried.Gerlach@draeger.com>

src/test/java/ca/uhn/fhir/jpa/starter/CustomBeanTest.java

@@ -11,7 +11,7 @@ import org.springframework.boot.test.context.SpringBootTest;
 		// "hapi.fhir.enable_repository_validating_interceptor=true",
 		"hapi.fhir.fhir_version=r4"
 })
-public class CustomBeanTest {
+class CustomBeanTest {
 
 	@Autowired
 	some.custom.pkg1.CustomBean customBean1;