[WIP] Implement Zitadel IDP

[TheBrambleShark]

Closes #350

This PR implements an Aspire integration to add support for the Zitadel IDP (https://zitadel.com).

PR Checklist

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• PR doesn't include merge commits (always rebase on top of our main, if needed)
• New integration
  • Docs are written
  • Added description of major feature to project description for NuGet package (4000 total character limit, so don't push entire description over that)
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Every new API (including internal ones) has full XML docs
• Code follows all style conventions

Other information

[TheBrambleShark]

This PR contains a couple missing features currently:

• Docs have yet to be written
• Tests have yet to be written
• There is no integration with a CockroachDB or PostgreSQL database for Zitadel to store data.
• Health check has not yet been implemented.

I had these in my original code, but it seems to have been lost to time so I've needed to recreate it from scratch.

[aaronpowell]

Does it ship specific version numbers? If so, can we pin it so that we ensure consistent behaviour over time.

[TheBrambleShark]

It appears they have a mix of actual version numbers and generated ids. The generated ids appear to be builds for specific PRs/branches so I think we can ignore those.

How should we handle pinning these? Are you thinking a static class with const strings or an enum? Or do you mean just ship it with an explicit version as the tag rather than latest?

Edit: Here is the current latest version (not counting the hash value tags) https://github.com/zitadel/zitadel/pkgs/container/zitadel/376730503?tag=v2.66.14

[aaronpowell]

We should align with the release that is published as latest - https://github.com/zitadel/zitadel/releases

Currently, that is v2.71.4