@Override
    public String transform(final String formUserId) {
        val result = formUserId.trim();
        return this.toUpperCase ? result.toUpperCase(Locale.ENGLISH) : result.toLowerCase(Locale.ENGLISH);
    }
A transformer that converts the form uid to either lowercase or
uppercase. The result is also trimmed. The transformer is also able
to accept and work on the result of a previous transformer that might
have modified the uid, such that the two can be chained.

@author Misagh Moayyed
@since 4.1.0
core/cas-server-core-util-api/src/main/java/org/apereo/cas/util/transforms/ConvertCasePrincipalNameTransformer.java