explicitly declare \Stringable interface (#47697)

according to the [PHP docs](https://www.php.net/manual/en/class.stringable.php):

> Stringable is implicitly present on any class that has the magic __toString() method defined, although it can and should be declared explicitly.

The return types of the `__toString()` methods are inconsistent, but I skipped addressing that now, because I'm not exactly clear on how we're handling that in the framework.

Author: browner12

src/Illuminate/Auth/Access/Response.php

@@ -3,8 +3,9 @@
 namespace Illuminate\Auth\Access;
 
 use Illuminate\Contracts\Support\Arrayable;
+use Stringable;
 
-class Response implements Arrayable
+class Response implements Arrayable, Stringable
 {
     /**
      * Indicates whether the response was allowed.

src/Illuminate/Broadcasting/Channel.php

@@ -3,8 +3,9 @@
 namespace Illuminate\Broadcasting;
 
 use Illuminate\Contracts\Broadcasting\HasBroadcastChannel;
+use Stringable;
 
-class Channel
+class Channel implements Stringable
 {
     /**
      * The channel's name.

src/Illuminate/Database/Eloquent/Model.php

@@ -22,8 +22,9 @@
 use Illuminate\Support\Traits\ForwardsCalls;
 use JsonSerializable;
 use LogicException;
+use Stringable;
 
-abstract class Model implements Arrayable, ArrayAccess, CanBeEscapedWhenCastToString, HasBroadcastChannel, Jsonable, JsonSerializable, QueueableEntity, UrlRoutable
+abstract class Model implements Arrayable, ArrayAccess, CanBeEscapedWhenCastToString, HasBroadcastChannel, Jsonable, JsonSerializable, QueueableEntity, Stringable, UrlRoutable
 {
     use Concerns\HasAttributes,
         Concerns\HasEvents,

src/Illuminate/Http/Client/Response.php

@@ -6,8 +6,9 @@
 use Illuminate\Support\Collection;
 use Illuminate\Support\Traits\Macroable;
 use LogicException;
+use Stringable;
 
-class Response implements ArrayAccess
+class Response implements ArrayAccess, Stringable
 {
     use Concerns\DeterminesStatusCode, Macroable {
         __call as macroCall;

src/Illuminate/Mail/Transport/ArrayTransport.php

@@ -3,12 +3,13 @@
 namespace Illuminate\Mail\Transport;
 
 use Illuminate\Support\Collection;
+use Stringable;
 use Symfony\Component\Mailer\Envelope;
 use Symfony\Component\Mailer\SentMessage;
 use Symfony\Component\Mailer\Transport\TransportInterface;
 use Symfony\Component\Mime\RawMessage;
 
-class ArrayTransport implements TransportInterface
+class ArrayTransport implements Stringable, TransportInterface
 {
     /**
      * The collection of Symfony Messages.

src/Illuminate/Mail/Transport/LogTransport.php

@@ -3,12 +3,13 @@
 namespace Illuminate\Mail\Transport;
 
 use Psr\Log\LoggerInterface;
+use Stringable;
 use Symfony\Component\Mailer\Envelope;
 use Symfony\Component\Mailer\SentMessage;
 use Symfony\Component\Mailer\Transport\TransportInterface;
 use Symfony\Component\Mime\RawMessage;
 
-class LogTransport implements TransportInterface
+class LogTransport implements Stringable, TransportInterface
 {
     /**
      * The Logger instance.

src/Illuminate/Mail/Transport/SesTransport.php

@@ -5,12 +5,13 @@
 use Aws\Exception\AwsException;
 use Aws\Ses\SesClient;
 use Exception;
+use Stringable;
 use Symfony\Component\Mailer\Header\MetadataHeader;
 use Symfony\Component\Mailer\SentMessage;
 use Symfony\Component\Mailer\Transport\AbstractTransport;
 use Symfony\Component\Mime\Message;
 
-class SesTransport extends AbstractTransport
+class SesTransport extends AbstractTransport implements Stringable
 {
     /**
      * The Amazon SES instance.

src/Illuminate/Mail/Transport/SesV2Transport.php

@@ -5,12 +5,13 @@
 use Aws\Exception\AwsException;
 use Aws\SesV2\SesV2Client;
 use Exception;
+use Stringable;
 use Symfony\Component\Mailer\Header\MetadataHeader;
 use Symfony\Component\Mailer\SentMessage;
 use Symfony\Component\Mailer\Transport\AbstractTransport;
 use Symfony\Component\Mime\Message;
 
-class SesV2Transport extends AbstractTransport
+class SesV2Transport extends AbstractTransport implements Stringable
 {
     /**
      * The Amazon SES V2 instance.

src/Illuminate/Pagination/AbstractCursorPaginator.php

@@ -14,12 +14,13 @@
 use Illuminate\Support\Str;
 use Illuminate\Support\Traits\ForwardsCalls;
 use Illuminate\Support\Traits\Tappable;
+use Stringable;
 use Traversable;
 
 /**
  * @mixin \Illuminate\Support\Collection
  */
-abstract class AbstractCursorPaginator implements Htmlable
+abstract class AbstractCursorPaginator implements Htmlable, Stringable
 {
     use ForwardsCalls, Tappable;
 

src/Illuminate/Pagination/AbstractPaginator.php

@@ -8,12 +8,13 @@
 use Illuminate\Support\Collection;
 use Illuminate\Support\Traits\ForwardsCalls;
 use Illuminate\Support\Traits\Tappable;
+use Stringable;
 use Traversable;
 
 /**
  * @mixin \Illuminate\Support\Collection
  */
-abstract class AbstractPaginator implements Htmlable
+abstract class AbstractPaginator implements Htmlable, Stringable
 {
     use ForwardsCalls, Tappable;