Add textual representation entities for Fronius status codes

[farmio]

Proposed change

Refactorings to make it possible to have multiple entities for a single API response field:

• optionally decouple EntityDescription.key from API response key
• Add optional value_fn to EntityDescriptions eg. to be able to map a API response value to a different value (status_code -> message)

New entities:

• Inverter staus_message is a textual, translatable representation of "status_code" integer
• Meter meter_location_description is a textual, translatable representation of "meter_location" integer

Changed features:

• OhmPilots status_message entity state is now translatable (this was previously hardcoded english in the lib pyfronius)

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:
• Link to documentation pull request:

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[home-assistant]

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

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[rorso]

In case this gets adopted and there is a commitment to try this with the error codes too - these are part of the user manual.
They cover a bunch of additional devices that talk to the inverter - which serves as the general data mediator.

I assume they would be quite universal within the Fronius Ecosphere, at least for all "Symo" variants. Not all error codes may apply for all devices. If you do not have a hybrid model, "battery" errors do not apply. I have a different model than the listed document, but at least I successfully could match a handful of error numbers with this document. 306, 307 are to expected, 461 may happen occasionally.

I was not able not verify this in detail however. Fortunately most of those errors are not that common. 😬

https://www.fronius.com/~/downloads/Solar%20Energy/Operating%20Instructions/42,0426,0222,DE.pdf
https://www.fronius.com/~/downloads/Solar%20Energy/Operating%20Instructions/42,0426,0222,EN.pdf

I cannot help with the coding, but I could help with the boring stuff like translating the PDF-doc into a suitable table.

[weitzelb]

I'd suggest on having a look at handling invalid error code responses in the same way.

Not exposing the complexity and simplify use through a generic function is probably helpful for future expandability (should there be a need/thought to do so). Not crucial in my opinion though.

[weitzelb]

Looks good to me. For those edge cases not covered by the test, they could be added later as well. Looks in working order.

[emontnemery]

LGTM, thanks @farmio 👍