Limit rainbird aiohttp client session to a single connection

[allenporter]

Proposed change

Limit rainbird aiohttp client session to a single connection so that any concurrent requests are queued rather than issued in parallel. This should fix any issues with rainbird stability due to concurrent requests either from the data coordinator, UI, or automations.

Manually tested:

• Without this change: If you spam the sprinkler switch on and off over and over again it will fail with an error due to the device being busy
• With the change: If you spam the sprinkler switch on and off over and over again it always succeeds.

Additionally manually tested config flows, adding and removing/disabling the config entries, etc and verifying all connections are closed properly.

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 Rainbird integration is loosing connection when switches are used in automation #111708
• This PR is related to issue:
• 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.

[home-assistant]

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

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[MartinHjelmare]

Probably close the session on Home Assistant stop too.

[allenporter]

I considered this, but intentionally left this out because it seemed like a lot of code with unclear benefit to me. I think it makes sense for a connection pool with thousands of connections, but for a single connection it seemed fine to just wait for unload? I've sent PR #112292 however since you've asked for it.

[MartinHjelmare]

What do you mean "to just wait for unload"?