Implement database authentication support.

config/config.example.json

@@ -3,7 +3,10 @@
 
   "database": {
     "address": "127.0.0.1:27017",
-    "name": "studybot"
+    "name": "studybot",
+    "auth": true,
+    "username": "admin",
+    "password": "foobar"
   },
 
   "web": {

src/models/config.ts

@@ -19,6 +19,9 @@ export interface Config {
 export interface DatabaseConfig {
   address: string;
   name: string;
+  auth: boolean;
+  username?: string;
+  password?: string;
 }
 
 export interface WebConfig {

src/services/config.ts

@@ -64,6 +64,14 @@ export class ConfigService {
     if (!this.config.database.name) {
       throw Error("The database name is missing or empty.");
     }
+    if(this.config.database.auth) {
+      if(!this.config.database.username) {
+        throw Error("Database auth is enabled but username is missing or empty.");
+      }
+      if(!this.config.database.password) {
+        throw Error("Database auth is enabled but password is missing or empty.");
+      }
+    }
   }
 
   private static validateWebConfig(): void {

src/services/database/database.ts

@@ -1,13 +1,19 @@
-import mongoose, { Connection, Mongoose } from "mongoose";
 import { DatabaseConfig } from "models/config";
+import mongoose, { Connection, Mongoose } from "mongoose";
 
 export class DatabaseService {
   private static mongooseInstance: Mongoose;
 
   public static async connect(dbConfig: DatabaseConfig) {
+    const auth: {user: string, password: string} | undefined = !dbConfig.auth ? undefined : {
+      user: dbConfig.username,
+      password: dbConfig.password
+    }; 
+
     this.mongooseInstance = await mongoose.connect(`mongodb://${dbConfig.address}/${dbConfig.name}`, {
       useNewUrlParser: true,
       useUnifiedTopology: true,
+      auth
     });
   }