Add metadata support to Snapcast media players

[mill1000]

Proposed change

Add metadata support to Snapcast media players.

Snapcast streams can contain metadata provided via a stream plugin or natively.

Snapcast includes metadata support for the following sources:

• Librespot via stream plugin
• Mopidy via stream plugin
• MPD via stream plugin
• Airplay natively

Additionally I have developed a stream plugin for UPnP renderers: https://github.com/mill1000/snapcast-upnp

Example Screenshots
UPnP Stream Plugin

Airplay Native

This is a redo of my original PR #117372 which was split into multiple phases.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes # N/A
• This PR is related to issue: N/A
• Link to documentation pull request: N/A

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• [N/A] Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• [N/A] The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• [N/A] New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• [N/A] For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[home-assistant]

Hey there @luar123, mind taking a look at this pull request as it has been labeled with an integration (snapcast) you are listed as a code owner for? Thanks!

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[joostlek]

Snapcast includes support for the following sources

The integration or the software/devices?

[mill1000]

Snapcast includes support for the following sources

The integration or the software/devices?

The software.

[home-assistant]

Please take a look at the requested changes, and use the Ready for review button when you are done, thanks 👍

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[mill1000]

@joostlek Any additional concerns with this change?

[joostlek]

In general I think I like to have tests for this so we can be sure that it works like we expect, but that's not a hard requirement

[mill1000]

Ok, add some tests to check the metadata properties and some basic media player state. Plenty to expand upon as well.

I ended up switching back to Mapping[str, Any]] for the metadata property as I couldn't make mypy happy with the more complex type hint.

[chriscn]

@mill1000 would you like any help on this, think this would be a massive value add for a lot of people using the snapcast integration.

[mill1000]

Sure! Any help would be appreciated.

I'm not aware of any additional requested changes to this PR. I think it just needs final approval and to be merged.