docs: 4.4 Content-Type charset + drop dead Symfony <=6.4 branch (#2329)

* docs(content-negotiation): document 4.4 charset change

Since 4.4 (core #8226), Content-Type only gets `; charset=utf-8`
for text/* and application/xml; JSON-family media types no longer
carry it. Verified against formatContentType() in
src/State/Util/HttpResponseHeadersTrait.php at upstream/4.4.

* docs(serialization): drop unreachable Symfony <=6.4 branch

Symfony floor is ^7.4 || ^8.0 since core #8397 (verified in
src/Symfony/composer.json at upstream/4.4), so the annotations
branch is unreachable and the >=7.0 branch is unconditional.
Collapse both into a single attributes-only instruction.

* docs(getting-started): state PHP/Symfony version floor

No page stated the supported versions. Add PHP >=8.2 and
Symfony ^7.4 || ^8.0, taken from composer.json and
src/Symfony/composer.json at upstream/4.4.

Author: soyuka

core/content-negotiation.md

@@ -420,3 +420,37 @@ API Platform automatically adds two HTTP headers to responses for resources:
 
 > See [LDP §4.2 / Primer notes on Accept-Post](https://www.w3.org/TR/ldp/#Accept-Post) and typical
 > exposure via OPTIONS.
+
+## Content-Type Charset
+
+> [!NOTE] Behavioral change in API Platform 4.4 (core
+> [#8226](https://github.com/api-platform/core/pull/8226)).
+
+Since 4.4, the `; charset=utf-8` parameter is only appended to the `Content-Type` response header
+for media types whose IANA registration actually defines a `charset` parameter: `text/*` types (for
+example `text/html`, `text/csv`, `text/xml`) and `application/xml`. JSON-based media types —
+`application/json`, `application/ld+json`, `application/hal+json`, `application/vnd.api+json`,
+`application/merge-patch+json`, `application/problem+json`, and so on — do not define a `charset`
+parameter (per RFC 8259, and the `+json` structured syntax suffix of RFC 6839) and are always UTF-8,
+so the parameter is no longer added to them.
+
+Before 4.4, `; charset=utf-8` was appended unconditionally to every response, including JSON-based
+formats. For example, for a JSON-LD response:
+
+```diff
+- Content-Type: application/ld+json; charset=utf-8
++ Content-Type: application/ld+json
+```
+
+An XML response is unaffected, as `application/xml` still gets the parameter:
+
+```http
+Content-Type: application/xml; charset=utf-8
+```
+
+> [!WARNING] If a client or a test asserts on the exact `Content-Type` header value for a JSON-based
+> format, it will break after upgrading to 4.4: the `charset=utf-8` suffix is gone. Update those
+> assertions accordingly.
+
+The rule is implemented in `formatContentType()` in
+[`HttpResponseHeadersTrait`](https://github.com/api-platform/core/blob/4.4/src/State/Util/HttpResponseHeadersTrait.php).

core/getting-started.md

@@ -5,6 +5,8 @@
 You can choose your preferred stack between Symfony, Laravel, or bootstrapping the API Platform core
 library manually.
 
+API Platform requires PHP 8.2 or higher. The Symfony variant requires Symfony `^7.4` or `^8.0`.
+
 > [!CAUTION] If you are migrating from an older version of API Platform, make sure you read the
 > [Upgrade Guide](upgrade-guide.md).
 

core/serialization.md

@@ -62,45 +62,15 @@ Just like other Symfony and API Platform components, the Serializer component ca
 using attributes, XML or YAML. Since attributes are easy to understand, we will use them in the
 following examples.
 
-> [!NOTE] If you are not using the API Platform Symfony variant, you need to enable annotation
-> support in the serializer configuration as outlined below, depending on your Symfony version.
-
-#### Configuration for Symfony `<= 6.4`
-
-##### General Case
+> [!NOTE] If you are not using the API Platform Symfony variant, you need to enable attribute
+> support in the serializer configuration as outlined below.
 
 Add the following configuration to your `framework.yaml` file:
 
 ```yaml
 # api/config/packages/framework.yaml
 framework:
-    serializer: { enable_annotations: true }
-```
-
-##### Using Symfony Flex
-
-If you use [Symfony Flex](https://github.com/symfony/flex) and Symfony `<= 6.4`, simply run the
-following command:
-
-```console
-composer req doctrine/annotations
-```
-
-You're all set!
-
-#### Configuration for Symfony `>= 7.0`
-
-If you are using Symfony >= 7.0,
-[annotations have been replaced by attributes](https://www.doctrine-project.org/2022/11/04/annotations-to-attributes.html).
-
-Update your configuration as follows:
-
-```diff
-# api/config/packages/framework.yaml
-
-framework:
--  serializer: { enable_annotations: true }
-+  serializer: { enable_attributes: true }
+    serializer: { enable_attributes: true }
 ```
 
 #### Additional Syntax Configuration for All Versions