Allow a calculated action on a to-one relation

[delchev]

A to-one relation could not express a DERIVED default. init: covers the fixed case (a literal target seed id), but nothing covered "read it off another record" — a sales document's currency defaulting from its company's base currency. The adjacent hooks all fall short by design: dependsOn is a UI-only cascade that never fires on a server-side create, and the setRelationField process step takes a literal id too.

Authoring calculatedActionOnCreate on a relation looked like it should work and silently did nothing: the typed mapping is Gson, which ignores unknown properties, so the key was dropped at parse time with no error — the #6541 family, one level up from seed rows.

Changes

• RelationIntent gains calculatedActionOnCreate/OnUpdate + isCalculated().
• New shared EdmIntentGenerator.putCalculatedAction emits isCalculatedProperty plus the action names from BOTH relation builders (same-model relationProperty and crossModelRelationProperty).
• The DAO template needed NO change: a relation is already an ordinary property in the .model — the FK column, typed to the target's key — so the template's shared property loop and its actionAssign macro emit entity.<Relation> = Beans.get(<class>.class).calculate(entity); against the Integer FK with no new branch. The gap was engine-only, so consuming it needs a jar swap and no registry re-seed.
• The parser rejects the combinations where there is no single FK to assign or the value is not the author's to set: a collection relation, a composition parent (preset by the layout), and an EntityStatus badge (owned by the workflow transitions — init: is its starting-value hook).

Tests

• EdmIntentGeneratorTest asserts the three emitted keys on both builders and that an action-less relation stays unmarked.
• IntentParserTest asserts the key binds onto the model (the typed-mapping test is the regression guard for the silent drop) and that a collection relation is rejected.
• Full engine-intent suite: 406 green.
• Verified at the runtime layer against a live instance: five document repositories emit the call; a REST create omitting Currency defaults it from the company's base currency, an explicitly posted Currency is respected, and a defaulted invoice + a currency-less payment auto-allocate end to end (ISSUED → PAID).

Owed: an IntentEmissionCoverageIT case — the fixture has no calculated action of either kind today, and adding one needs a compilable custom/ class in the emission-test project; left for a change that can run that gate.

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