Add upgrade instructions

Author: GromNaN

UPGRADE-2.16.md

@@ -47,6 +47,25 @@ Calling `Doctrine\ODM\MongoDB\Configuration::setProxyDir()` or
 `Doctrine\ODM\MongoDB\Configuration::getProxyDir()` is deprecated and triggers
 a deprecation notice when using native lazy objects.
 
+## `TypeRegistry` replace `Type::getType()` and `Type::hasType()`
+
+A new `Doctrine\ODM\MongoDB\Types\TypeRegistry` class has been introduced
+to manage custom types. The static methods of `Doctrine\ODM\MongoDB\Types\Type`
+are deprecated and will be removed in MongoDB ODM 3.0:
+- `Type::getType($name)` → `TypeRegistry::getType($name)`
+- `Type::hasType($name)` → `TypeRegistry::hasType($name)`
+- `Type::addType($name, $class)` → `TypeRegistry::addType($name, $class)`
+- `Type::getTypesMap()` → `TypeRegistry::getTypesMap()`
+- `Type::registerType()` → `TypeRegistry::registerType()`
+- `Type::overrideType()` → `TypeRegistry::registerType()`
+- `Type::getTypeFromPHPVariable()` → `TypeRegistry::guessTypeFromValue()`
+- 'Type::convertPHPToDatabaseValue()` → `TypeRegistry::convertToDatabaseValue()`'
+
+You can set and get the `TypeRegistry` instance from the `Doctrine\ODM\MongoDB\Configuration`
+using `getTypeRegistry()` and `setTypeRegistry()`.
+
+To access the type of mapped field, use the `ClassMetadata::getFieldType()` method.
+
 ## Override `Type::closureToPHP()` for custom type classes
 
 The default implementation of `Doctrine\ODM\MongoDB\Types\Type::closureToPHP()`

src/Persisters/DocumentPersister.php

@@ -1383,7 +1383,7 @@ private function prepareQueryExpression(array $expression, ClassMetadata $class)
     /**
      * Checks whether the value has DBRef fields.
      *
-     * This method doesn't check if the the value is a complete DBRef object,
+     * This method doesn't check if the value is a complete DBRef object,
      * although it should return true for a DBRef. Rather, we're checking that
      * the value has one or more fields for a DBref. In practice, this could be
      * $elemMatch criteria for matching a DBRef.
@@ -1400,7 +1400,7 @@ private function hasDBRefFields($value): bool
             $value = get_object_vars($value);
         }
 
-        foreach ($value as $key => $value) {
+        foreach ($value as $key => $v) {
             if ($key === '$ref' || $key === '$id' || $key === '$db') {
                 return true;
             }

src/Types/Type.php

@@ -134,7 +134,7 @@ public static function getType(string $type): Type
     /**
      * Get a Type instance based on the type of the passed php variable.
      *
-     * @deprecated Will be removed in 3.0
+     * @deprecated Use {@see TypeRegistry::guessTypeFromValue()} instead
      *
      * @param mixed $variable
      */