code: public String getWarningReport() {
  		Map<String, List<PropertyMigration>> content = getContent(
  				LegacyProperties::getRenamed);
  		if (content.isEmpty()) {
  			return null;
  		}
  		StringBuilder report = new StringBuilder();
  		report.append(String.format("%nThe use of configuration keys that have been "
  				+ "renamed was found in the environment:%n%n"));
  		append(report, content);
  		report.append(String.format("%n"));
  		report.append("Each configuration key has been temporarily mapped to its "
  				+ "replacement for your convenience. To silence this warning, please "
  				+ "update your configuration to use the new keys.");
  		report.append(String.format("%n"));
  		return report.toString();
  	}
docs: Return a report for all the properties that were automatically renamed. If no such
  properties were found, return {@code null}.
  @return a report with the configurations keys that should be renamed