fix(Relation): support updating relation without initial value

[kettanaito]

GitHub

• Fixes Cannot update relation if not initially defined #137

Root cause

The issue occurred because relation was applied only when parsing the model. So if it wasn't provided an initial value, the entire application was skipped:

data/src/model/defineRelationalProperties.ts

Lines 24 to 27 in cf67f57

	if (!get(initialValues, propertyPath)) {
	log('relation has no initial value, skipping...')
	continue
	}

This meant that when you update a parent entity, its relational property (Relation instance) didn't have source set at all, throwing an exception. This is not correct, even relational properties without initial values must be applied.

Changes

• Relation is no longer resolved when applied.
• All relations are applied when defining relational properties, but only those with initial values are resolved. This sets the necessary target/source properties on the Relation instance but does not define a proxy getter property.
• Rewrites relation test to assert exact data structures (makes tests more precise).

[kettanaito]

relation.source.modelName is not yet set.