[viessmann] refactor channel commands and add units

[rogrun]

This PR has following changes:

• Refactor channel command handling
• Add units for KilowattPeak, Volt, Ampere, WattHour, meter, degree
• Extended logging of unknown unit
• Add support for hygiene function
• Fix commands for holiday channels

[lsiepel]

@rogrun not sure if i asked before, but it would be appreciated if PR's are kept small, by seperating the bug fixes, refactoring and enhancements. This would make it simpler to review, backport, list changes in the release notes seperate and reduces the possibility of regressions.

[Copilot]

Pull request overview

This PR refactors the command handling for the Viessmann binding's device channels and adds support for several new physical units. It introduces a more generic, data-driven approach to parsing API commands using the new FeatureCommand/FeatureCommandParams DTOs, replacing the previous hard-coded FeatureCommands class with a flexible Map<String, FeatureCommand>. It also adds support for hygiene functions, fixes holiday channel commands, and improves timezone-awareness for scheduling.

Changes:

• Replaces the monolithic FeatureCommands DTO with a generic map-based FeatureCommand model and refactors the entire command dispatch pipeline in DeviceHandler
• Adds new channel types for watt-hour, kilowattpeak, volt, ampere, meter, degree, duration-minute, start-hour, and start-minute; adds new StoredChannelValues class for state caching across command calls
• Fixes holiday channel command handling and adds hygiene function support; uses openHAB's configured timezone via ViessmannUtil.getOpenHABZoneId() replacing LocalTime.now() calls

Reviewed changes

Copilot reviewed 57 out of 57 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
thing-types.xml	Adds new channel types for new units and bumps thing type version to 5
viessmann.properties	Fills in blank i18n entries and adds command labels for hygiene mode values
ViessmannUtil.java	Replaces old resource-reading helpers with hyphenToCamel() and timezone-aware getOpenHABZoneId()
JsonUtil.java + GsonJsonElementSerializer.java	New Jackson-based JSON utilities for serializing Gson JsonElement trees (used for debug logging)
ViessmannGatewayHandler.java	Delegates feature-update logic to ViessmannAccountHandler, makes linkRegistry nullable
ViessmannBridgeHandler.java	Uses openHAB timezone for API call reset window
ViessmannAccountHandler.java	Centralizes feature-loading logic, injects installationId into FeatureDataDTO
DeviceHandler.java	Major refactor of command handling and feature update processing; adds hygiene and holiday support
FeatureDataDTO.java	Adds toPrettyJson() for anonymized debug output
FeatureProperties.java	Adds custom Gson deserializer for flexible/additional properties; adds new fields
FeatureCommand.java + FeatureCommandParams.java + FeatureCommandParamType.java	New generic command model
StoredChannelValues.java	New class to cache channel values for multi-param command assembly
ThingMessageDTO.java	Updated to use Map<String, FeatureCommand>
ViessmannBindingConstants.java	Adds new unit map entries and constants
BindingServlet.java	Null-safety fix for User-Agent header
ViessmannApi.java	Encoding and logging improvements
Various deleted DTO files	Removed granular command/parameter DTOs replaced by generic model

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[rogrun]

@rogrun not sure if i asked before, but it would be appreciated if PR's are kept small, by seperating the bug fixes, refactoring and enhancements. This would make it simpler to review, backport, list changes in the release notes seperate and reduces the possibility of regressions.

@lsiepel Thanks for the reminder. I’ll try to keep future PRs smaller and separate bug fixes, refactorings and enhancements where possible to make reviews and backports easier.

[lsiepel]

Thanks, i have just two comments left

[lsiepel]

Thanks LGTM