Add Umami hosting integration

[Odonno]

Add the Umami (https://umami.is/) hosting integration, a web analytics solution that can be self-hosted simply with a SQL backend storage.

Note: only PostgreSQL is currently supported as a backend storage.

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

• I have added a new WithStorageBackend extension method, not sure if that follows the current convention
• Tested locally with the example project, via the Blazor web app example
• I tweaked the code to make cross-container communication working with Podman. I am not sure what is the best practice at the moment (reading the connection string & supporting both Docker & Podman)
• I had some compilation errors with the newly created Blazor app. I am not sure why this is happening. I might go for a simple Vite app.

[aaronpowell]

Just a few questions about the design, and it looks like the integration test isn't passing.

[aaronpowell]

I assume that this is only for something you want in this demo app and not something you'd need to do all the time right?

[Odonno]

Yes, this is for demo purpose.