refactor: add declare strict_types to all classes in ./src (#758)

* refactor: add declare strict_types to all classes in ./src

* fix: correct regression from adding declare strict_types

* refactor: enforce string at datetime casting

* docs: add changelog entry

Author: DannyvdSluijs

CHANGELOG.md

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema;
 
 use JsonSchema\Exception\InvalidArgumentException;

src/JsonSchema/ConstraintError.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the JsonSchema package.
  *

src/JsonSchema/Constraints/BaseConstraint.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the JsonSchema package.
  *

src/JsonSchema/Constraints/CollectionConstraint.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the JsonSchema package.
  *

src/JsonSchema/Constraints/ConstConstraint.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the JsonSchema package.
  *

src/JsonSchema/Constraints/Constraint.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the JsonSchema package.
  *

src/JsonSchema/Constraints/ConstraintInterface.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the JsonSchema package.
  *

src/JsonSchema/Constraints/EnumConstraint.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the JsonSchema package.
  *

src/JsonSchema/Constraints/Factory.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * This file is part of the JsonSchema package.
  *
@@ -174,7 +176,7 @@ public function check(&$element, $schema = null, ?JsonPointer $path = null, $i =
 
     protected function validateDateTime($datetime, $format)
     {
-        $dt = \DateTime::createFromFormat($format, $datetime);
+        $dt = \DateTime::createFromFormat($format, (string) $datetime);
 
         if (!$dt) {
             return false;