As a user, I want to modify the changes message in the email notifications.
This is useful when a change contains a message in xml.

For example:

• Given a change with the message <defectId>DEFECT-666</defectId><message>Initial commit</message>
• When I define the content of the email notifications as follows: ${CHANGES, regex="<defectId>(DEFECT-[0-9]+)</defectId><message>(.*)</message>", replace="[$1] $2"}
• Then I should get an email notification with the following content: [DEFECT-666] Initial commit