Add mail transport agent into Docker container

[castorsky]

What

Add msmtp as mail transport agent into Docker container.

This PR adds mstmp and msmtp-mta packages and configuration script into docker image to setup msmtp with environment variables. Tested only with Google mail provider.

How to use

One can configure MTA with variables in compose file or include env-file into compose file:

...
  gvmd:
    image: greenbone/gvmd:stable
    environment:
      - MTA_HOST=smtp.gmail.com
      - MTA_PORT=587
      - MTA_TLS=on
      - MTA_STARTTLS=on
      - MTA_AUTH=on
      - MTA_USER=<username>
      - MTA_FROM=<username>@gmail.com
      - MTA_PASSWORD=<some_password>
...

Why

At the time containerized GVMD can not send alerts and notifications via email.

References

As someone said in the Greenbone Forum it is worth to add sending email ability into container.

[ilyesm]

Hi there! Any feedback regarding this PR? Any plans for it to be included in the future?

[bjoernricks]

Hey,

I've thought about this PR in detail yesterday evening and I am willing to include the MTA in the gvmd container image for the next release. Could you therefore resolve the following things:

• rebase the PR and include the latest changes from main
• adjust the commit messages for containing a conventional commit that gets listed in the release changelog
• calculate how much bigger the container image gets with the MTA and add it to the PR description
• add a PR to extend the community docs on how to setup the MTA. A new section at the container workflows would be nice similar to https://greenbone.github.io/docs/latest/22.4/container/workflows.html#exposing-gvmd-unix-socket-for-gmp-access

[github-actions]

Conventional Commits Report

😢 No conventional commits found.

👉 Learn more about the conventional commits usage at Greenbone.

[castorsky]

I have made something weird in an attempt of rewriting the old commit message and messed all up. Will open new PR.