fix: update action to support relationship lookups

[davenewza]

Previously we could only call update and delete using inputs targeting fields on the direct model, but with recent changes we can now support relationships to lookup and filter by.

For example, the following action performs

• a lookup by composite unique fields,
• a lookup using fields in a nested model, and
• filtering by related model fields.

update deactivateProduct(productCode, brand.code) {
  @set(product.isActive = false)
  @where(product.isActive)
  @where(product.supplier.isRegistered)
  @permission(expression: ctx.identity.user in product.brand.editors)
}

The following SQL will be generated for such a query:

UPDATE "product" 
SET is_active = ? 
FROM "brand" AS "product$brand" 
LEFT JOIN "supplier" AS "product$supplier" ON "product$supplier"."id" = "product"."supplier_id" 
WHERE 
  "product$brand"."id" = "product"."brand_id" AND 
  "product"."product_code" IS NOT DISTINCT FROM ? AND 
  "product$brand"."code" IS NOT DISTINCT FROM ? AND 
  "product"."is_active" IS NOT DISTINCT FROM ? AND 
  "product$supplier"."is_registered" IS NOT DISTINCT FROM ? 
RETURNING "product".*