Billing: Allow users to add custom member modifiers before VAT

Elwig/Resources/Sql/27-28.sql

@@ -0,0 +1,13 @@
+-- schema version 27 to 28
+
+ALTER TABLE payment_custom ADD COLUMN mod_abs INTEGER DEFAULT NULL;
+ALTER TABLE payment_custom ADD COLUMN mod_rel REAL DEFAULT NULL;
+ALTER TABLE payment_custom ADD COLUMN mod_comment TEXT DEFAULT NULL;
+
+PRAGMA writable_schema = ON;
+
+UPDATE sqlite_schema SET sql = REPLACE(REPLACE(sql, 'amount  INTEGER NOT NULL', 'amount      INTEGER DEFAULT NULL'), 'comment TEXT', 'comment     TEXT    DEFAULT NULL')
+WHERE type = 'table' AND name = 'payment_custom';
+
+PRAGMA schema_version = 2701;
+PRAGMA writable_schema = OFF;