1. payerEmail attribute is null when options undefined.
2. payerEmail attribute is null when requestPayerEmail is undefined.
3. payerEmail attribute is null when requestPayerEmail is false.
4. payerEmail attribute is 'wpt@w3.org' when requestPayerEmail is true.
5. payerEmail attribute is 'wpt@w3.org' when requestPayerEmail is truthy.