Bug 30120: Save and apply extended attributes during self registration verification...

Bug 30120: Save and apply extended attributes during self registration verification by email

The self registration form stores a new borrower as a borrower modification when verifying by email.

Borrower modifications can  handle extended attributes.

This patch simply sotres the extended attributes in the modifications table, and approves a modification
to the extended attributes only after patron is created

To test:
1 - Apply patch
2 - Create a patron attribute and set it as viewable/editable in the OPAC
3 - Set system preference PatronSelfRegistrationVerifyByEmail
4 - Reigster a new patron on the OPAC, provide an email and populate the extended attribute
5 - Retrieve the verification token, the last on in the messages table
    SELECT * FROM message_queue;
6 - Go tot he url from above
7 - Confirm successful patron creation
8 - View patron record and confirm attribute was set

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>