Allow video stream preview in generic camera config flow

[davet2001]

Proposed change

Add preview of video stream during config flow to allow user to verify stream settings when configuring.

The generic camera config flow was updated some time ago to show a preview of the still image before the config flow was complete, the aim was to help users get username/passwords correct without having to add a camera, then delete it if it didn't work. But so far that was only implemented on still images.

The real problem and most of the remaining questions that still occur on the forums are from users trying to set up cameras, and confusing rtsp settings, passwords, or simply not knowing how to find a valid stream URL for their camera.

This feature has been a goal of mine for some time but finally got round to it last weekend!

Attention points for reviewer (feedback wanted):

• The aim is to set up a camera stream during one of the config flow steps without actually adding it to the hass object. This is done by creating the GenericCamera object, then immediately creating a stream URL for it. But I'm not sure if this is an ok thing to do...
  • We could possibly be left with a left over stream at the end (I can't see a big problem with this - it should disappear on restart),
  • I'm not fully sure of the consequences of creating a Camera but not adding it to the hass object properly.

Note that the above only concerns the stream preview. The final configured camera is unchanged by this PR.

I've tested it manually and added pytests.

A related frontend PR was needed to enable <ha-hls-player> to be shown during the config flow.

Once this is merged, I'll do a separate PR to add the same functionality to the options flow.

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 #
• This PR is related to issue: Allow video streams to be shown in markdown frontend#21246
• Link to documentation pull request:

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:

• Documentation added/updated for www.home-assistant.io

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

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

To help with the load of incoming pull requests:

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

[davet2001]

@hunterjm Would value your thoughts on this one!

[frenck]

There is a merge conflict, can you take a look?

../Frenck

[davet2001]

Replaced with #122563