[hibernate#712] Minor code clean up

* Replace deprecated method calls
* Remove some Idea warnings
* Replace with method reference
* Change to static class a test entity

Author: DavideD

hibernate-reactive-core/src/main/java/org/hibernate/reactive/mutiny/impl/MutinySessionImpl.java

@@ -54,7 +54,7 @@ <T> Uni<T> uni(Supplier<CompletionStage<T>> stageSupplier) {
 	@Override
 	public Uni<Void> flush() {
 //		checkOpen();
-		return uni( () -> delegate.reactiveFlush() );
+		return uni( delegate::reactiveFlush );
 	}
 
 	@Override

hibernate-reactive-core/src/test/java/org/hibernate/reactive/FindAfterFlushTest.java

@@ -74,9 +74,7 @@ public void withTransactionFindAfterFlushWithStages(TestContext context) {
 						.persist( wc )
 						.thenCompose( $ -> s.flush() )
 						.thenCompose( $ -> s.find( Webcomic.class, wc.getId() ) )
-						.thenAccept( found -> {
-							context.assertEquals( wc, found );
-						} )
+						.thenAccept( found -> context.assertEquals( wc, found ) )
 				)
 		);
 	}
@@ -87,8 +85,8 @@ public void withTransactionFindAfterFlushWithMutiny(TestContext context) {
 		test( context, getMutinySessionFactory()
 				.withTransaction( (s, tx) -> s
 						.persist( wc )
-						.then( () -> s.flush() )
-					  	.then( () -> s.find( Webcomic.class, wc.getId() ) )
+						.call( () -> s.flush() )
+					  	.chain( () -> s.find( Webcomic.class, wc.getId() ) )
 					  	.invoke( found -> {
 							context.assertEquals( wc, found );
 						} )
@@ -157,7 +155,7 @@ public int hashCode() {
 
 		@Override
 		public String toString() {
-			return new StringBuilder( title ).append( " by " ).append( creator ).toString();
+			return title + " by " + creator;
 		}
 	}
 }

hibernate-reactive-core/src/test/java/org/hibernate/reactive/StageExceptionsTest.java

@@ -54,7 +54,7 @@ public void testDuplicateKeyException(TestContext context) {
 	}
 
 	@Entity
-	public class MyPerson {
+	public static class MyPerson {
 
 		@Id
 		public String name;