Smarter commodity-context defaults and Commitment commodity field

[Flix6x]

Description

New in-scope features for the multi-commodity flex-context (follow-up to #2172, stacked on #2271) ahead of the v1 release.

Commitment schema commodity field

• CommitmentSchema gets an undocumented commodity field, defaulting to electricity, for internal bookkeeping — matching a commitment to the device(s) sharing that commodity. Not the documented way for API users to associate a commitment with a commodity; that remains the multi-commodity commodities list, one context per commodity.

Smarter defaults for commodity contexts

A commodity context that omits grid-connection fields now gets sensible defaults instead of raising or leaving the grid unconstrained, based on which fields are explicitly given:

• Nothing given (e.g. bare {"commodity": "gas"}, no grid connection): zero site-consumption-capacity and zero site-production-capacity as soft constraints, unlimited site-power-capacity.
• Only consumption-price given: unlimited site-power-capacity and site-consumption-capacity, 0 site-production-capacity.
• Only production-price given: unlimited site-power-capacity and site-production-capacity, 0 site-consumption-capacity.
• Only site-consumption-capacity given: unlimited site-power-capacity, that consumption capacity, 0 consumption-price, 0 site-production-capacity (and 0 production-price).
• Only site-production-capacity given: unlimited site-power-capacity, that production capacity, 0 production-price, 0 site-consumption-capacity (and 0 consumption-price).
• Only site-power-capacity given: hard constraint at that capacity; site-consumption/production-capacity equal to it; 0 consumption- and production-price.

A relax-constraints: False context that ends up with a smart-defaulted 0 hard capacity now logs a warning, since this can make the schedule infeasible.

Correctness fix (found while implementing the above)

• A commodity context with no user-given price fields was stamped with a fallback "EUR" currency, which could spuriously trip cross-commodity currency-mismatch checks against a differently-currencied portfolio. Such price-free contexts are now tagged and excluded from the mismatch check; their fallback-currency fields get re-expressed under the portfolio's real currency once it's known (from a top-level price or a sibling commodity context).
• StorageScheduler.convert_to_commitments now logs a warning when a commitment's commodity matches zero devices (aid for catching typos).

Regression tests

7 parametrized DB-free cases for the 6 smart-default cases (+ a multi-field combination); price-free-context currency handling (top-level price sets currency, sibling context sets currency, nothing given anywhere falls back to EUR, genuine mismatches still 422).

• Added changelog item in documentation/changelog.rst

How to test

pytest flexmeasures/data/schemas/tests/test_scheduling.py flexmeasures/data/models/planning/tests/test_commitments.py

Related Items

Stacked on #2271; follow-up to #2172; prepares #1946 for release.

[Flix6x]

Self-review.

[nhoening]

Very nice that we have this, another improvement to make flex-configuration have less unexplainable failures.
There might be new questions if things default to something, but at least we make it explicit, and this can also be read by LLMs which can hopefully offer useful answers.

[Flix6x]

Interaction note with #2279: the smart defaults fill a zero consumption-price into price-free commodity contexts, which defeats #2279's internal-node detection (a priceless commodity like a steam network should become a hard balance node). Tested fix on a local merge of both branches: record prices_are_defaulted in fill_grid_connection_defaults (this PR's code) and consume it in _prepare (#2279's code). I'll open the follow-up PR once both have landed; no change needed here.

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