@CanIgnoreReturnValue
    default AuthenticationBuilder mergeAttributes(final Map<String, List<Object>> toMerge) {
        toMerge.forEach(this::mergeAttribute);
        return this;
    }
Merge attribute.

@param toMerge the to merge
@return the authentication builder
api/cas-server-core-api-authentication/src/main/java/org/apereo/cas/authentication/AuthenticationBuilder.java