Drop integration for backups, email and Dropbox

[dennissiemensma]

Only for post-docker-migration of this project

See #1746 (comment)

All of the features dropped should be available one way or another using separate tools/containers. It gives total control to the end-users and drops quite some non-core-project code/features from this project.

[dennissiemensma]

E.g. replacing the backup code by simply this:

docker exec -e -it dsmr-db pg_dump -h localhost -U dsmrreader -d dsmrreader

Using Dropbox sync like:

• https://hub.docker.com/r/otherguy/dropbox/

Using this for relaying emails for sending backups:

• https://github.com/ix-ai/smtp

So many stuff is available and it greatly reduces maintainance for me, along that I'd really want to keep moving forward to smaller services, responsible for a single thing.

It's also the reason why I reject many feature requests for DSMR-reader, as they do not align with the core goal of this project.

[dennissiemensma]

Dropbox heeft de laatste tijd relatief veel kuren, dus des te meer reden om dit door te voeren. Ik weet namelijk niet wat erger is: Geen backups of denken dat je backups hebt en er dan achter komen dat ze er niet zijn...

[dennissiemensma]

https://workspaceupdates.googleblog.com/2023/09/winding-down-google-sync-and-less-secure-apps-support.html