Implement Mongo Seeder v2

What does this MR do?

Adds seeding to User and Questions databases with following env variables to control it:

• ENABLE_QUESTION_DB_SEEDING.
• ENABLE_USER_DB_SEEDING.

Testing

• Ensure ENABLE_QUESTION_DB_SEEDING is set to true in docker-compose.
• Ensure ENABLE_USER_DB_SEEDING is set to true in docker-compose.
• Ensure Docker's MongoDB instances have no documents in Users and Questions DBs.
• Run docker compose up --build.
• Login as with username 'admin' and password 'password'.
• Question appears on page.

Relevant issues

Fixes missing seeding.

backend-services/user-service/controllers/appController.js

@@ -33,7 +33,7 @@ export async function register(req, res) {
     const existUsername = new Promise((resolve, reject) => {
       UserModel.findOne({ username }, function (err, user) {
         if (err) reject(new Error(err));
-        if (user) reject({ error: "Please use unique username" });
+        if (user) reject({ error: "Username already exists!" });
 
         resolve();
       });
@@ -43,7 +43,7 @@ export async function register(req, res) {
     const existEmail = new Promise((resolve, reject) => {
       UserModel.findOne({ email }, function (err, email) {
         if (err) reject(new Error(err));
-        if (email) reject({ error: "Please use unique Email" });
+        if (email) reject({ error: "An account with that email address already exists!" });
 
         resolve();
       });
@@ -118,7 +118,7 @@ export async function login(req, res) {
           .compare(password, user.password)
           .then((passwordCheck) => {
             if (!passwordCheck)
-              return res.status(400).send({ error: "Don't have Password" });
+              return res.status(400).send({ error: "Incorrect username or password!" });
 
             // create jwt token
             const token = jwt.sign(