Discovered in this PR: https://github.com/DSpace/DSpace/pull/2719#issuecomment-611415255
Currently the MetadataExposureServiceImpl caches all the "metadata.hide.*" configurations in an internally stored Map: https://github.com/DSpace/DSpace/blob/master/dspace-api/src/main/java/org/dspace/app/util/MetadataExposureServiceImpl.java#L63
This means these settings are loaded once (when the MetadataExposureService first loads in Spring configs), and cached thereafter. So, changing the "metadata.hide.*" configurations after that fact has no effect (likely until Tomcat is rebooted).
This Service should be updated to no longer cache these configs and instead load them dynamically from the ConfigurationService, likely using the new `getPropertyKeys(String prefix)` method which would be much more efficient than the current code. See https://github.com/DSpace/DSpace/blob/master/dspace-services/src/main/java/org/dspace/servicemanager/config/DSpaceConfigurationService.java#L135