feat(lagoon): per-query collation for OrderBy, drop the database locale check

- lagoon.OrderBy takes variadic lagoon.OrderOption values; lagoon.Collate(name)
  emits a validated, double-quoted COLLATE clause (e.g. "pl-x-icu")
- remove the exported CheckLocale and the ICU pl-PL check from Open and Use
- framework test containers and per-test databases are plain PostgreSQL
- lagoon README, root README and docs pages drop the locale requirement;
  queries-and-pagination gains a "Sorting with a collation" section
  backed by ExampleCollate

docs/database/models.md

@@ -8,7 +8,7 @@ order: 10
 
 A WinterCMS model extends Eloquent and describes its behaviour with properties such as `$fillable`, `$hidden` and `$jsonable`. A SummerCMS model is a plain GORM struct in the plugin's `models` package, and [lagoon](../../modules/lagoon/README.md) supplies the Eloquent conventions that GORM does not have: allow-listed mass assignment, JSON and encrypted columns, Laravel-style validation and pagination.
 
-The data layer supports PostgreSQL only. `lagoon.Open` refuses a database whose default collation is not the ICU `pl-PL` locale (`lagoon.CheckLocale`), so text ordering is the same in every query without a `COLLATE` clause. Create the database with that locale, as shown in [Installation](../setup/installation.md).
+The data layer supports PostgreSQL only and puts no requirement on the database's default locale. A list that must sort text in one language's order passes a collation to `lagoon.OrderBy`, as described in [Queries and pagination](queries-and-pagination.md#sorting-with-a-collation).
 
 ## Defining a model