Remove DeclaredHandler to prevent accidental internal discovery

The `DeclaredHandler` has become a liability. Because class, interface, and enum
names are represented as strings, we run the risk of the library "helpfully"
identifying a piece of user input as an internal system part.

If a user happens to input a string that matches an internal class or enum name,
the stringifier would automatically confirm its existence by applying the
specialized formatting. This creates an information leakage vulnerability where
an outsider could map out our application's internal architecture simply by
guessing names.

By removing this handler, we ensure that a string is treated just as a string.
This follows our recent "secure-by-default" trend seen in the
`CallableStringifier` changes: we are prioritizing the privacy of the
application's internal blueprint over the convenience of automatic type
detection.

Author: henriquemoody

README.md

@@ -83,12 +83,6 @@ echo stringify(['foo' => true, 'bar' => 42, 'baz' => ['qux' => INF, 'quux' => nu
 echo stringify(tmpfile()) . PHP_EOL;
 // `resource <stream>`
 
-echo stringify(BasicEnumeration::FOO) . PHP_EOL;
-// `BasicEnumeration::FOO`
-
-echo stringify(BackedEnumeration::QUX) . PHP_EOL;
-// `BackedEnumeration::QUX`
-
 echo stringify(new WithProperties()) . PHP_EOL;
 // `WithProperties { +$publicProperty=true #$protectedProperty=42 -$privateProperty="something" }`
 
@@ -136,9 +130,6 @@ echo stringify(new RuntimeException()) . PHP_EOL;
 
 echo stringify(new InvalidArgumentException('This is the exception message')) . PHP_EOL;
 // `InvalidArgumentException { "This is the exception message" in file.php:112 }`
-
-echo stringify(Traversable::class) . PHP_EOL;
-// `Traversable`
 ```
 
 To see more examples of how to use the library check the [integration tests](tests/integration).

src/Handlers/CompositeHandler.php

@@ -41,7 +41,6 @@ public static function create(): self
             new ResourceHandler($quoter),
             new BoolHandler($quoter),
             new NullHandler($quoter),
-            new DeclaredHandler($quoter),
             $jsonEncodableHandler = new JsonEncodableHandler(),
         );
         $handler->prependHandler(