added basic support for Oracle.

Author: findinpath

ORACLE.md

@@ -0,0 +1,46 @@
+Testing hints for Oracle with testcontainers
+============================================
+
+Follow the guideline:
+
+https://blogs.oracle.com/oraclemagazine/deliver-oracle-database-18c-express-edition-in-containers
+
+for setting up an Oracle docker image.
+
+
+The initial setup of the image (due to large downloads) will probably take around 30 mins.
+
+Oracle docker images repository:
+
+https://github.com/oracle/docker-images
+
+Since the [Oracle-XE Module](https://www.testcontainers.org/modules/databases/oraclexe/)
+from [testcontainers](https://www.testcontainers.org/) doesn't work properly,
+a custom [OracleContainer](src/test/java/com/findinpath/connect/nestedset/jdbc/testcontainers/OracleContainer.java)
+has been developed for test purposes.
+
+The `system` user is a restricted Oracle user and when trying to connect with this user
+the following exception will be thrown:
+
+```
+ORA-12526, TNS:listener: all appropriate instances are in restricted mode
+``` 
+
+
+Workaround:
+
+Set a breakpoint on
+`org.testcontainers.containers.JdbcDatabaseContainer.createConnection`
+
+and after the database within the testcontainers test has started, execute the following script:
+
+```bash
+docker exec -it --user=oracle ${oracle_image_name} bash
+``` 
+
+```sqlplus
+sqlplus /nolog
+conn sys as sysdba
+password: oracle
+alter system disable restricted session;
+```