#19: added generate certificate and upload it to minio

faircommons-services/common/pom.xml

...ava/eu/fairkom/faircommons/common/minio/MinioService.java

faircommons-services/post-registration-service/pom.xml

...mons/post_registration/config/ThymeleafConfiguration.java

.../post_registration/listener/PostRegistrationListener.java

...ns/post_registration/service/PostRegistrationService.java

..._registration/service/RegistrationCertificateService.java