Add Switzerland OBIS fields for channel 1-1

[SebiGo]

Adds 34 DEFINE_FIELD entries for the AM550 smart meter (used by EWL Luzern): total energy (1-1:1.8.0 / 2.8.0), reactive energy totals (3.8.0 / 4.8.0), reactive energy by quadrant Q1-Q4 (5-8.8.0-2), per-phase active and reactive power (1-1:21-64.7.0), and maximum power demand with timestamp (1-1:1.6.0 / 2.6.0).

Specification from EWL

[SebiGo]

Hi, and thanks for maintaining this library!

A bit of context on this PR: I run a P1 reader on an Iskraemeco AM550 (the meter EWL Luzern deploys), which sends almost everything on the Swiss 1-1 channel. The existing _ch fields cover the totals and tariff registers, but per-phase power, reactive energy and the maximum-demand registers aren't mapped, so they can't be surfaced today without parsing the raw telegram by hand. This PR fills that gap.

That said, I'm not sure how well this matches the direction you'd want, so I'd rather ask than assume:

• Scope: I added the full set from EWL's OBIS table (34 fields, including per-phase reactive power and the Q1–Q4 reactive-energy quadrants). That may be more than you'd like to carry — happy to trim it to a leaner, more commonly useful subset.
• Naming: I followed the existing _ch convention as closely as I could, but I'll gladly rename anything to fit your scheme.
• Downstream: if you're happy to merge this, I'll follow up with the matching PR in esphome/esphome to expose these fields in the dsmr component's sensor.py, so they're actually usable end-to-end.

If this isn't a direction you want to support, no problem at all — just say the word and I'll close it. Otherwise I'm happy to revise it however works best for you.

[PolarGoose]

@SebiGo,

Thanks a lot for your work. I will process it today or tomorrow

[Copilot]

Pull request overview

This PR expands the parser’s Switzerland (channel 1-1) OBIS field coverage to support the AM550 smart meter profile (EWL Luzern) and updates the existing parser test to exercise and validate those new fields end-to-end.

Changes:

• Added Switzerland-specific OBIS field definitions for total active energy, reactive energy totals and quadrants (Q1–Q4), per-phase active/reactive power, and maximum demand with timestamp.
• Extended the comprehensive parsing test telegram with the corresponding 1-1:* OBIS lines.
• Added assertions verifying correct unit handling (including integer *Wh fallback) and timestamped maximum-demand parsing.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
src/dsmr_parser/fields.h	Adds Switzerland/channel 1-1 DEFINE_FIELD entries for AM550-specific OBIS codes (energy, reactive energy, per-phase power, max demand w/ timestamp).
tests/parser_test.cpp	Extends the full-message parsing test with new 1-1 OBIS lines and validates parsed values/timestamps.

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[PolarGoose]

@SebiGo,

Please create a pull request to EspHome and EspHome docs.

[SebiGo]

Thanks heaps!

• [dsmr] Document Switzerland channel 1-1 sensors (EWL Luzern AM550) esphome/esphome.io#6917
• [dsmr] add Switzerland channel 1-1 sensors (EWL Luzern AM550) esphome/esphome#17391