fix: add security provider in btp impl (#49)

src/main/java/eu/europa/ec/dgc/verifier/service/SignerCertificateDownloadBtpServiceImpl.java

@@ -32,13 +32,15 @@
 import eu.europa.ec.dgc.gateway.connector.dto.TrustListItemDto;
 import eu.europa.ec.dgc.gateway.connector.model.TrustListItem;
 import java.io.IOException;
+import java.security.Security;
 import java.security.cert.CertificateException;
 import java.time.ZonedDateTime;
 import java.util.ArrayList;
 import java.util.Base64;
 import java.util.List;
 import java.util.Objects;
 import java.util.stream.Collectors;
+import javax.annotation.PostConstruct;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import net.javacrumbs.shedlock.spring.annotation.SchedulerLock;
@@ -49,6 +51,7 @@
 import org.apache.http.util.EntityUtils;
 import org.bouncycastle.cert.CertException;
 import org.bouncycastle.cert.X509CertificateHolder;
+import org.bouncycastle.jce.provider.BouncyCastleProvider;
 import org.bouncycastle.operator.ContentVerifierProvider;
 import org.bouncycastle.operator.OperatorCreationException;
 import org.bouncycastle.operator.RuntimeOperatorException;
@@ -75,6 +78,11 @@ public class SignerCertificateDownloadBtpServiceImpl implements SignerCertificat
 
     private final SignerInformationService signerInformationService;
 
+    @PostConstruct
+    private void init() {
+        Security.addProvider(new BouncyCastleProvider());
+    }
+
     @Override
     @Scheduled(fixedDelayString = "${dgc.certificatesDownloader.timeInterval}")
     @SchedulerLock(name = "SignerCertificateDownloadService_downloadCertificates", lockAtLeastFor = "PT0S",