Fix json serialization

Account/Group.php

@@ -216,7 +216,7 @@ class Group implements ArrayableInterface, \JsonSerializable
      */
     public function __toString()
     {
-        return $this->jsonSerialize();
+        return json_encode($this->toArray());
     }
 
     /**
@@ -229,7 +229,7 @@ class Group implements ArrayableInterface, \JsonSerializable
      */
     public function jsonSerialize()
     {
-        return json_encode($this->toArray());
+        return $this->toArray();
     }
 
     /**

DataStorage/Database/DataMapperAbstract.php

@@ -660,12 +660,12 @@ class DataMapperAbstract implements DataMapperInterface
             return null;
         } elseif ($type === 'DateTime') {
             return $value->format('Y-m-d H:i:s');
-        } elseif ($type === 'json') {
+        } elseif ($type === 'Json' || $type === 'jsonSerializable') {
             return json_encode($value);
         } elseif ($type === 'Serializable') {
             return $value->serialize();
-        } elseif ($type === 'jsonSerializable') {
-            return $value->jsonSerializable();
+        } elseif ($value instanceof \JsonSerializable) {
+            return json_encode($value->jsonSerialize());
         } elseif (is_object($value)) {
             return $value->getId();
         } elseif ($type === 'int') {

Datatypes/Address.php

@@ -153,7 +153,7 @@ class Address implements \JsonSerializable
      */
     public function jsonSerialize(int $option = 0) : string
     {
-        return json_encode($this->toArray());
+        return $this->toArray();
     }
 
     /**

Datatypes/Location.php

@@ -247,7 +247,7 @@ class Location implements \JsonSerializable, \Serializable
      */
     public function jsonSerialize() : string
     {
-        return json_encode($this->toArray());
+        return $this->toArray();
     }
 
     /**

Message/Http/Header.php

@@ -63,8 +63,8 @@ class Header extends HeaderAbstract
 
         if (!$overwrite && isset($this->header[$key])) {
             return false;
-        } elseif ($overwrite && isset($this->header[$key])) {
-            if ($this->isSecurityHeader($key)) {
+        } elseif ($overwrite || !isset($this->header[$key])) {
+            if ($this->isSecurityHeader($key) && isset($this->header[$key])) {
                 throw new \Exception('Cannot change security headers.');
             }
 
@@ -166,7 +166,7 @@ class Header extends HeaderAbstract
      */
     public function get(string $key) : array
     {
-        return $this->header[$key] ?? [];
+        return $this->header[strtolower($key)] ?? [];
     }
 
     /**

Message/Http/Response.php

@@ -114,12 +114,15 @@ class Response extends ResponseAbstract implements RenderableInterface
      */
     public function render() : string
     {
-        switch ($this->header->get('Content-Type')) {
-            case MimeType::M_JSON:
+        $types = $this->header->get('Content-Type');
+
+        foreach($types as $type) {
+            if(stripos($type, MimeType::M_JSON) !== false) {
                 return $this->jsonSerialize();
-            default:
-                return $this->getRaw();
+            }
         }
+
+        return $this->getRaw();
     }
 
     /**
@@ -167,8 +170,8 @@ class Response extends ResponseAbstract implements RenderableInterface
                     $result += $response;
                 } elseif (is_scalar($response)) {
                     $result[] = $response;
-                } elseif ($response instanceof \Serializable) {
-                    $result[] = $response->serialize();
+                } elseif ($response instanceof \JsonSerializable) {
+                    $result[] = $response->jsonSerialize();
                 } else {
                     throw new \Exception('Wrong response type');
                 }

Stdlib/Collection/Collection.php

@@ -74,7 +74,7 @@ class Collection implements \Countable, \ArrayAccess, \Iterator, \JsonSerializab
      */
     public function jsonSerialize()
     {
-        return json_encode($this->collection);
+        return $this->collection;
     }
 
     /**