ExceptionInterface cannot be caught

Extends `ExceptionInterface` from `Throwable` so that consumers can catch the marker interface without static analysis errors.

Also marks all existing concrete exceptions as soft `@final` so that the next major can finalise them.

Signed-off-by: George Steel <[email protected]>

src/Exception/ExceptionInterface.php

@@ -4,6 +4,8 @@
 
 namespace Mezzio\Helper\Exception;
 
-interface ExceptionInterface
+use Throwable;
+
+interface ExceptionInterface extends Throwable
 {
 }

src/Exception/MalformedRequestBodyException.php

@@ -7,6 +7,7 @@
 use Exception;
 use InvalidArgumentException;
 
+/** @final */
 class MalformedRequestBodyException extends InvalidArgumentException implements ExceptionInterface
 {
     /** @param string $message */

src/Exception/MissingHelperException.php

@@ -7,6 +7,7 @@
 use DomainException;
 use Psr\Container\ContainerExceptionInterface;
 
+/** @final */
 class MissingHelperException extends DomainException implements
     ContainerExceptionInterface,
     ExceptionInterface

src/Exception/MissingRouterException.php

@@ -7,6 +7,7 @@
 use DomainException;
 use Psr\Container\ContainerExceptionInterface;
 
+/** @final */
 class MissingRouterException extends DomainException implements
     ContainerExceptionInterface,
     ExceptionInterface

src/Exception/RuntimeException.php

@@ -4,6 +4,7 @@
 
 namespace Mezzio\Helper\Exception;
 
+/** @final */
 class RuntimeException extends \RuntimeException implements ExceptionInterface
 {
 }