Verify email addresses to prevent login & signup with non-existing email

[samuko-things]

Issue description

In the API server, a user can signup or login with an invalid email (i.e an email that is not real or does not exist in google Gmail, Microsoft Outlook, yahoo, etc database). We want to correct this.

Expected behaviour

• At signup, user's email should be verified before the user is stored on the database.
• a confirmation message should be sent to the user's email for verification.
• The email verification must be successful before the user can be stored in the database.
• the email_verified property must be set to true after verification before the user can be stored on the database.

Additional context

• Repo URL: https://github.com/collabo-community/api-server

Testing checklist

Note (to contributor taking on this task assignment): Add the testing checklist below (without this note) to your pull request when submitting your fix. This will guide (you and) the contributors who will review your fix to know what is important to check or test for.

• At signup, user's email is verified before the user is stored on the database.
• A confirmation message is sent to the user's email for verification.
• The email verification is successful before the user is stored in the database.
• The email_verified property is set to true after verification before the user is stored on the database.
• I certify that I ran my checklist