Resolve "voucher types"

Closes #187 (closed)

added 5 commits

• bbad0e1a - voucher type structuctures
• 2950842f - formatting
• 335f2d68 - language use correct form
• 87a725b0 - message text corrected
• 856ce904 - forms for editing voucher types and prices

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unmarked as a Work In Progress

added 3 commits

• 47f28f7f - unused code removed
• f6f913ec - unit tests for voucher_type view
• 531324ce - unit tests for voucher_type_price views

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enabled an automatic merge when the pipeline for 531324ce succeeds

merged

mentioned in commit e0f64f3b