Docker MTA

[buchi]

Provide MTA container for handling mail. Handles incoming and outgoing mail with Postfix.
This is meant for setups where we deploy only containers and replaces the functionality provided by Postfix installed on the host.

Additionaly the mail host can now be configured through the follwing environment variables:

- SMTP_HOST
- SMTP_PORT
- SMTP_USER
- SMTP_PASSWORD
- SMTP_FORCE_TLS
- SMTP_NO_TLS

For [CA-XXXX]

Checklist

Everything has to be done/checked. Checked but not present means the author deemed it unnecessary.

• Changelog entry
• Link to issue (Jira or GitHub) and backlink in issue (Jira)

Only applicable should be left and checked.

• Upgrade-Steps:
  • SQL Operations do not use imported model (see docs)
  • Make it deferrable if possible
  • Execute as much as possible conditionally
  • DB-Schema migration
    • All changes on a model (columns, etc) are included in a DB-schema migration.
    • Constraint names are shorter than 30 characters (Oracle)
• API change:
  • Documentation is updated
  • API Changelog entry (see guide)
  • If breaking:
    • api-change label added
    • #delivery channel notified about breaking change
    • Scrum master is informed
• Bug fixed:
  • Resolved any Sentry issues caused by this bug
• New functionality:
  • for document also works for mail
  • for task also works for forwarding
• Further improvements needed:
  • Create follow-up stories and link them in the PR and Jira issue
• Change could impact client installations, client policies need to be adapted
• New translations
  • All msg-strings are unicode
• Change in schema definition:
  • If missing_value is specified, then default has to be set to the same value