Add option to disable keep-alive for Enphase Envoy connections

[catsmanac]

Proposed change

Add configuration option to Enphase Envoy integration to allow disabling keep-alive on the httpx connections to the Envoy. The option is disabled by default, user can enable it

Envoy firmware 3.18.10 observations show that obtaining data from the endpoint /api/v1/production/inverters is prone to failures with connection pool enabled. Until now this is the only firmware reporting this.

Observations from network packet traces:

• The communication is using httpx 0.27.0 with digest authentication.
• When a get from the endpoint is requested, the Envoy returns a 401 with the digest information included.
• HTTPX then repeats the get request on the same connection with the digest now included.
• The Envoy replies with TCP FIN,ACK to the message and closes the connection using RST.
• HTTPX signals a RemoteProtocolError.
• HTTPX repeats the get, new connection is build, but Digest is not included.
• Same sequence repeats up-to 4 times when tenacity limit is reached.

Test shows that setting the client to max_keepalive_connections=0 solves the issue.

Test with a recent ENVOY standard non-metered firmware 8.2.4264 using the disable keep-alive show no issues.

It is not clear if this is an httpx issue or not, the question is raised. As the firmware is pretty old fixes to httpx may not apply or not occur. It will take time for sure, for now adding the option will solve the issue for the HA user on short notice.

Type of change

• [ ] Dependency upgrade
• [x] 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 #126162
• This PR is related to issue:
• Link to documentation pull request: https://github.com/home-assistant/home-assistant.io/pull/35083

Checklist

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

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

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