Allow a 'service user' like www-data to login via ssh on Ubuntu or Debian

There are three things to do to allow a 'service user' like www-data to login via ssh.

DISCLAIMER:
READ EVERYTHING BEFORE USE ANY COMMAND... OTHERWISE, YOU MIGHT LOSE ACCESS OF YOUR SERVER...

#Step 01
########################
#Use the below GIST and propely follow the command then come here and use below steps.
Link: https://gist.github.com/mhrubel/43825450cba521ede15d7b73cf865472

#Step 02
########################
# Set a password for www-data
sudo passwd www-data 

#Step 03
########################
# Define a shell for www-data by editing /etc/passwd.
sudo nano /etc/passwd
# Replace
/usr/sbin/nologin or similar by /bin/bash

# on the line of all of the user. EX: root or any other user you want to use to login on your server...

Note: You might not be able to login with "root" or any other user,
      # if you do not add /bin/bash for all of the user, you wish to use for login...

### Lets Restart the SSHD service
sudo systemctl restart sshd
# OR
sudo service sshd restart

NOTE: This guide should work with almost all Ubuntu and Debian based OS versions...

DISCLAIMER: I'm not responsible if you brake anything from the server using this guide! Use this guide at YOUR OWN RISK...

This solution most probably works in all of the versions of Ubuntu and Debian OS. But, I only used it with the Ubuntu 18.04 version...