added some endpoint tests

...n/api/dto/database/DatabaseContainerCreateRequestDto.java

.../api/dto/database/DatabaseContainerCreateResponseDto.java

fda-container-managing-service/pom.xml

...java/at/tuwien/endpoints/DatabaseContainerController.java

...-service/src/test/java/at/tuwien/BaseIntegrationTest.java

...ervice/src/test/java/at/tuwien/endpoint/EndpointTest.java

...rc/test/java/at/tuwien/service/DockerIntegrationTest.java

...-service/src/test/java/at/tuwien/service/ServiceTest.java

...rvices/src/main/java/at/tuwien/entity/ContainerImage.java

...c/main/java/at/tuwien/mapper/DatabaseContainerMapper.java

...ces/src/main/java/at/tuwien/service/ContainerService.java