feat: rewrite repositories with base entity repository class.

feat: sales and purchases status.
feat: sales and purchases auto-increment number.
fix: settings find query with extra columns.

server/src/database/migrations/20200719152005_create_bills_table.js

@@ -12,6 +12,7 @@ exports.up = function(knex) {
     table.decimal('amount', 13, 3).defaultTo(0);
     table.decimal('payment_amount', 13, 3).defaultTo(0);
     table.string('inv_lot_number').index();
+    table.date('opened_at').index();
     table.integer('user_id').unsigned();
     table.timestamps();
   });