Configure echoCTF.RED to use Google Mail

In order to configure echoCTF.RED to use a GMail account for sending emails you first have to configure the GMail account.

1. Go to https://myaccount.google.com/
2. Enable 2-step verification
3. Go to https://myaccount.google.com/apppasswords (NOTE: this do not work without 2-step verification)
4. Create an application ie myplatform
5. Copy the generated app password, it will look something like blah blah blah blah
6. Go to your echoCTF backend Settings => Configure
7. Scroll to the Mail Setting section and add something like the following gmail+smtp://YOUR_GOOGLE_MAIL:APP_PASSWORD@default?local_domain=YOUR_DOMAIN&verify_peer=0
8. Replace YOUR_GOOGLE_MAIL with your gmail eg blah.blah@gmail.com
9. Replace APP_PASSWORD with the application password you copied from step 5 but without spaces in between eg blahblahblahblah
10. Replace YOUR_DOMAIN with your platform frontend domain eg ctf.blah.io
11. Press Save
12. Execute composer require symfony/google-mailer from your frontend and backend system folders