Added `checkEnvironmentVariables` function

src/utils/db.js

 'use strict';
 
-const grace                                     = require('./grace');
-const {createError, logError, logInfo, logWarn} = require('./log');
+const {checkEnvironmentVariables} = require('./util');
 
-['MONGODB_URI', 'SEQID_GEN_API'].forEach(varname => {
-	if (!process.env[varname]) {
-		logError(`Environment variable ${varname} is not defined!`);
-		grace.shutdown(1);
-	}
-});
+checkEnvironmentVariables('MONGODB_URI', 'SEQID_GEN_API');
 
-const {MongoClient} = require('mongodb');
-const SeqidGenApi   = require('@gviagroup/seqid-gen-api');
+const {MongoClient}                             = require('mongodb');
+const SeqidGenApi                               = require('@gviagroup/seqid-gen-api');
+const grace                                     = require('./grace');
+const {createError, logError, logInfo, logWarn} = require('./log');
 
 let   mongoClient = null;
 const seqidGen    = new SeqidGenApi(process.env.SEQID_GEN_API);

src/utils/util.js

 'use strict';
 
+const {shutdown} = require('./grace');
+const {logError} = require('./log');
+
 module.exports = {
 	
+	checkEnvironmentVariables(...varNames) {
+		for (const varName of varNames) {
+			if (!process.env[varName]) {
+				logError(`Environment variable ${varName} is not set!`);
+				shutdown(1);
+			}
+		}
+	}
+	
 };