Add getInstance to TypeSystem (#1323)

* Add getInstance to TypeSystem

* Update name

* Update diff

Author: injectives

driver/clirr-ignored-differences.xml

@@ -391,4 +391,10 @@
         <differenceType>3003</differenceType>
     </difference>
 
+    <difference>
+        <className>org/neo4j/driver/types/TypeSystem</className>
+        <differenceType>7012</differenceType>
+        <method>org.neo4j.driver.types.TypeSystem getDefault()</method>
+    </difference>
+
 </differences>

driver/src/main/java/org/neo4j/driver/types/TypeSystem.java

@@ -18,6 +18,8 @@
  */
 package org.neo4j.driver.types;
 
+import static org.neo4j.driver.internal.types.InternalTypeSystem.TYPE_SYSTEM;
+
 import org.neo4j.driver.util.Experimental;
 import org.neo4j.driver.util.Immutable;
 
@@ -28,6 +30,15 @@
 @Immutable
 @Experimental
 public interface TypeSystem {
+    /**
+     * Returns an instance of type system.
+     *
+     * @return instance of type system
+     */
+    static TypeSystem getDefault() {
+        return TYPE_SYSTEM;
+    }
+
     Type ANY();
 
     Type BOOLEAN();

driver/src/test/java/org/neo4j/driver/types/TypeSystemTest.java

@@ -21,6 +21,7 @@
 import static org.hamcrest.CoreMatchers.not;
 import static org.hamcrest.core.Is.is;
 import static org.hamcrest.junit.MatcherAssert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.neo4j.driver.Values.value;
 import static org.neo4j.driver.internal.types.InternalTypeSystem.TYPE_SYSTEM;
 
@@ -75,6 +76,11 @@ private TypeVerifier newTypeVerifierFor(Type type) {
         return new TypeVerifier(type, allValues);
     }
 
+    @Test
+    void shouldReturnTypeSystem() {
+        assertEquals(TYPE_SYSTEM, TypeSystem.getDefault());
+    }
+
     @Test
     void shouldNameTypeCorrectly() {
         assertThat(TYPE_SYSTEM.ANY().name(), is("ANY"));