feat: add support for specifying smtp server

[adrian549092]

Description

No issue associated with this feature but could be a solution for #370
The proposed change allows the user to specify an smtp server ip address or fqdn and port in the .env file to use for sending email and sms notifications. In my particular situation, the application resides behind a proxy server which does not allow connections to external smtp servers but I do have a local mail relay agent available for sending emails.

Testing

When SMTP_ADDRESS and SMTP_PORT are left unspecified the application will use the default gmail service and works as normal. When the mentioned variables are set then the application will use the specified settings to connect to an SMTP Relay Agent and send emails. Both of the previously mentioned cases were tested using the available test:notification npm script and I also set the PHONE_NUMBER and PHONE_CARRIER variables in order to confirm that SMS notifications worked as well. All tests succeeded.

SMTP_ADDRESS="<IP ADDRESS OF SMTP SERVER>"
SMTP_PORT=<TCP PORT FOR SMTP SERVER>

[jef]

Thanks for taking care of the conflicts. It was quite a bit 😅