Follow each binary format's UTF-8 rule: strict writers (CBOR/UBJSON/BJData/BSON), lenient readers (#5741)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/features/binary_formats/cbor.md

@@ -189,15 +189,16 @@ The library maps CBOR types to JSON value types as follows:
     ([RFC 8392](https://www.rfc-editor.org/rfc/rfc8392.html)), cannot be read with this library and need a
     general-purpose CBOR library instead.
 
-!!! warning "UTF-8 validation of text strings"
+!!! warning "Ill-formed UTF-8 in text strings"
 
-    [RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings
-    (major type 3) to be valid UTF-8. This library validates the bytes of every text string (object keys included) at
-    decode time and rejects ill-formed UTF-8 with a
-    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with
-    `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting value is
-    dumped. Byte strings (major type 2) are unaffected and are never validated, since they are not required to hold
-    text.
+    [RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings (major
+    type 3) to be valid UTF-8, but leaves it up to the decoder whether to enforce this. This library does not:
+    `from_cbor()` accepts a text string (object keys included) whose bytes are not valid UTF-8 and hands them back
+    unchanged. However, [`dump()`](../../api/basic_json/dump.md) still requires valid UTF-8 and throws
+    [`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) for such a value, unless an error handler is
+    passed that replaces or ignores the ill-formed bytes. By default, `to_cbor()` writes such a value back unchanged; if
+    [`JSON_STRICT_BINARY_UTF8`](../../api/macros/json_strict_binary_utf8.md) is enabled, it throws the same exception
+    instead. Byte strings (major type 2) are unaffected, since they are not required to hold text.
 
 !!! warning "Tagged items"