Improve/enhance the CMT example with use of TransactionAttributeType.REQUIRES_NEW

* Explain duplicate behavior
* add example of TransactionAttributeType.REQUIRES_NEW
* make it clear why the adding of the customer failed
* validate the customer name with a more logic constraint: letters & '-'
* add tests for the name matching function

Signed-off-by: Gerke - Ephorus <gerke.ephorus@gmail.com>