Convert backend to ESM

- About 5 years overdue
- Remove eslint, use bomejs instead

backend/migrations/20190215115310_customlocations.js

@@ -1,5 +1,6 @@
-const migrate_name = 'custom_locations';
-const logger       = require('../logger').migrate;
+import { migrate as logger } from "../logger.js";
+
+const migrateName = "custom_locations";
 
 /**
  * Migrate
@@ -8,17 +9,17 @@ const logger       = require('../logger').migrate;
  * @see http://knexjs.org/#Schema
  *
  * @param   {Object}  knex
- * @param   {Promise} Promise
  * @returns {Promise}
  */
-exports.up = function (knex/*, Promise*/) {
-	logger.info('[' + migrate_name + '] Migrating Up...');
+const up = (knex) => {
+	logger.info(`[${migrateName}] Migrating Up...`);
 
-	return knex.schema.table('proxy_host', function (proxy_host) {
-		proxy_host.json('locations');
-	})
+	return knex.schema
+		.table("proxy_host", (proxy_host) => {
+			proxy_host.json("locations");
+		})
 		.then(() => {
-			logger.info('[' + migrate_name + '] proxy_host Table altered');
+			logger.info(`[${migrateName}] proxy_host Table altered`);
 		});
 };
 
@@ -26,10 +27,11 @@ exports.up = function (knex/*, Promise*/) {
  * Undo Migrate
  *
  * @param   {Object}  knex
- * @param   {Promise} Promise
  * @returns {Promise}
  */
-exports.down = function (knex, Promise) {
-	logger.warn('[' + migrate_name + '] You can\'t migrate down this one.');
+const down = (_knex) => {
+	logger.warn(`[${migrateName}] You can't migrate down this one.`);
 	return Promise.resolve(true);
 };
+
+export { up, down };