Added support for Datatables

Added support for ajax-based server side validation (useful for validation of emails, duplicate usernames, etc.)
User form more or less ready in the basic version (i.e. without permission management)

lib/dt-helpers.js

@@ -0,0 +1,54 @@
+'use strict';
+
+const knex = require('../lib/knex');
+
+async function ajaxList(params, queryFun, columns) {
+    return await knex.transaction(async (tx) => {
+        const query = queryFun(tx);
+
+        const recordsTotalQuery = query.clone().count('* as recordsTotal').first();
+        const recordsTotal = (await recordsTotalQuery).recordsTotal;
+
+        query.where(function() {
+            let searchVal = '%' + params.search.value.replace(/\\/g, '\\\\').replace(/([%_])/g, '\\$1') + '%';
+            for (let colIdx = 0; colIdx < params.columns.length; colIdx++) {
+                const col = params.columns[colIdx];
+                if (col.searchable === 'true') {
+                    this.orWhere(columns[parseInt(col.data)], 'like', searchVal);
+                }
+            }
+        });
+
+        const recordsFilteredQuery = query.clone().count('* as recordsFiltered').first();
+        const recordsFiltered = (await recordsFilteredQuery).recordsFiltered;
+
+        query.offset(parseInt(params.start));
+
+        const limit = parseInt(params.length);
+        if (limit >= 0) {
+            query.limit(limit);
+        }
+
+        query.select(columns);
+
+        for (const order of params.order) {
+            query.orderBy(columns[params.columns[order.column].data], order.dir);
+        }
+
+        const rows = await query;
+        const rowsOfArray = rows.map(row => Object.keys(row).map(key => row[key]));
+
+        const result = {
+            draw: params.draw,
+            recordsTotal,
+            recordsFiltered,
+            data: rowsOfArray
+        };
+
+        return result;
+    });
+}
+
+module.exports = {
+    ajaxList
+};