Upgrade traefik to v3.0. Added postgres support

[robertvanlienden]

What

This PR adds PostgreSQL support to traefik/our development proxy.

Also upgrades traefik to 3.0. This was needed, but I've found no breaking changes in the setup see comment below...

How to test

Feel free to reach out to me (on Slack) if you have any questions.

I already have some project working with this development proxy setup to show.

[robertvanlienden]

Bummer; Was testing out with some project with multiple host names, and I am afraid that multiple hostnames are not working anymore the way we used to do it.

https://doc.traefik.io/traefik/v3.0/routing/routers/#rule

[quintenbuis]

@robertvanlienden Any new developments on this? Still seems like a useful feature.

[eXistenZNL]

@robertvanlienden any updates on this or can we close this PR?

[robertvanlienden]

@eXistenZNL I really would like to merge this some day. The biggest win, is that after this upgrade, we also can connect to databases trough Development Proxy!
Do we want to expose meer of minder ports? I would like minder!

The problem; This will be some breaking change (existing projects will be broken after this update).
My idea now; Maybe we can create some separate URL (current) for the traefik 2.0 proxy and after merging this create some new URL for the 3.0 proxy.
That way, we can upgrade projects to the 3.0 proxy when we want.

[quintenbuis]

Creating a new url can be done easily, since the url is only a redirect to a raw.githubcontent.com url. Create a v2 branch with these breaking changes and that should fix it.