Deprecate extending schema classes

Author: morozov

UPGRADE.md

@@ -8,6 +8,15 @@ awareness about deprecated code.
 
 # Upgrade to 4.4
 
+## Deprecated extension of schema classes
+
+Extending the following classes has been deprecated. Use them directly.
+
+- `Schema`
+- `Sequence`
+- `Table`
+- `View`
+
 ## Deprecated features of `Table::getIndexes()`, `Table::getUniqueConstraints()` and `Table::getForeignKeys()`
 
 Using the keys of the arrays returned by `Table::getIndexes()`, `Table::getUniqueConstraints()` and

src/Schema/Schema.php

@@ -52,6 +52,7 @@
  * execute them. Only the queries for the currently connected database are
  * executed.
  *
+ * @final
  * @extends AbstractAsset<UnqualifiedName>
  */
 class Schema extends AbstractAsset

src/Schema/Sequence.php

@@ -15,6 +15,7 @@
 /**
  * Sequence structure.
  *
+ * @final
  * @extends AbstractNamedObject<OptionallyQualifiedName>
  */
 class Sequence extends AbstractNamedObject

src/Schema/Table.php

@@ -38,6 +38,7 @@
 /**
  * Object Representation of a table.
  *
+ * @final
  * @extends AbstractNamedObject<OptionallyQualifiedName>
  */
 class Table extends AbstractNamedObject

src/Schema/View.php

@@ -11,6 +11,7 @@
 /**
  * Representation of a Database View.
  *
+ * @final
  * @extends AbstractNamedObject<OptionallyQualifiedName>
  */
 class View extends AbstractNamedObject