Document Symfony 8.x compatibility status and Behat ecosystem blocker

Adds notes explaining:
- Bundle code is Symfony 8.x-compatible
- Test suite is capped at Symfony 7.x by behat/behat and
  friends-of-behat/symfony-extension not yet supporting ^8.0
- Symfony 8.2 null-for-typed-string behaviour and the AP4 nullable
  metadata interaction that requires ?string + nullable ORM column

Author: silverbackdan

CLAUDE.md

@@ -100,6 +100,8 @@ This factory (`src/ApiPlatform/Metadata/Resource/RoutingPrefixResourceMetadataCo
 - **`application/problem+json`** is the correct Content-Type for any 4xx/5xx response generated by AP4's exception handler (`rfc_7807_compliant_errors: true` is the default in AP4 4.x). Only responses serialised normally (non-exception path) carry `application/ld+json`.
 - **Constraint constructors** (`Count`, `Length`, `NotBlank`, etc.) must use named arguments in Symfony 8.x — the array-options style (`new Count(['min' => 1])`) throws `TypeError`. Use `new Count(min: 1, minMessage: '...')`.
 - **`api_sub_level` context**: when normalising a sub-object (e.g. `ResourceMetadata` inside `MetadataNormalizer`), set `$context['api_sub_level'] = true`. Without it, `PartialCollectionViewNormalizer` injects a `"view": {"@type": "PartialCollectionView"}` entry into any array property whenever the request URI has query parameters, turning the array into a JSON object.
+- **Symfony 8.2 null-for-typed-string**: Symfony 8.2 converts a null value for a non-nullable typed string property into a proper validation violation rather than a raw TypeError. Prefer `?string = null` (nullable PHP type + nullable ORM column) so null passes through deserialization to the `#[Assert\NotBlank]` validator consistently across all Symfony versions. AP4's `AbstractItemNormalizer` reads serializer metadata (including the ORM `nullable` flag), so `?string` with `nullable: false` on the ORM column still triggers the TypeError path.
+- **Behat / Symfony 8.x**: The `behat/behat` and `friends-of-behat/symfony-extension` packages do not yet support Symfony 8.x (their constraints cap at `^7.0`). This holds `symfony/console`, `symfony/event-dispatcher`, `symfony/property-access`, `symfony/http-kernel`, and the full security stack at 7.x in the test environment. The production bundle code is Symfony 8.x-compatible; only the test tooling is blocked. Watch for a `behat/behat` 4.x stable release or updated `friends-of-behat/symfony-extension` to unblock.
 
 ### Serialization groups
 

README.md

@@ -15,6 +15,11 @@
 
 ### **[Read the documentation](https://docs.api.cwa.rocks/)**
 
+## Requirements
+
+- PHP 8.2+
+- Symfony 7.4+ (bundle code is Symfony 8.x-compatible; test suite is currently capped at Symfony 7.x by `behat/behat` and `friends-of-behat/symfony-extension` not yet supporting Symfony 8.x)
+
 ## Sponsors
 
 [![Blackfire](./docs/images/blackfire-io_secondary_horizontal_transparent.png)](https://blackfire.io/)