make DBTest.db propected, so that users won't accidentally static imp…

…ort it

jdbc-test/src/DBTest.kt

@@ -18,7 +18,7 @@ abstract class DBTest {
       startDevDB()
     }
 
-    val db: DataSource by lazy { DBModule().dataSource }
+    @JvmStatic protected val db: DataSource by lazy { DBModule().dataSource }
   }
 
   @BeforeEach open fun startTx() {