OZG-6499 Fix Spring cloud config client configuration

alfa-server/src/main/resources/application.yml

@@ -24,7 +24,7 @@ spring:
           issuer-uri: ${ozgcloud.oauth2.issuer-uri}
           jwk-set-uri: ${spring.security.oauth2.resourceserver.jwt.issuer-uri}/protocol/openid-connect/certs
   config:
-    import: optional:${ozgcloud_administration_address:http://localhost:8888/configserver/}
+    import: optional:configserver:${ozgcloud_administration_address:http://localhost:8888/configserver/}
 
 server:
   http2:

alfa-service/src/main/java/de/ozgcloud/alfa/postfach/PostfachProperties.java

@@ -12,7 +12,7 @@ import lombok.Setter;
 @RefreshScope
 @Getter
 @Setter
-class PostfachProperties {
+public class PostfachProperties {
 
 	static final String PREFIX = "ozgcloud.postfach";