Resolve "voucher functionality"

Closes #182 (closed)

added 7 commits

• 113fedfc - validator for social security number added
• df5c970d - voucher data structure
• 5e5afa60 - forms and views for creatng and editing vouchers
• a7f6a1dc - unit test for voucher to string methods
• 7c27133b - unit test for voucher type to string methods
• f793badf - unit tests for voucher views
• 1ed1d7a5 - unit tests for voucher forms

Compare with previous version

unmarked as a Work In Progress

enabled an automatic merge when the pipeline for 1ed1d7a5 succeeds

mentioned in commit 8fb46044

merged