Added documentation

Signed-off-by: Andrew DeMaria <lostonamountain@gmail.com>

documentation/DATABASE.md

@@ -0,0 +1,73 @@
+# Database Configuration
+
+*Before doing anything, make sure your database is properly backed up. Ensure your server is shutdown*
+
+Libresonic has the capability to override the database settings. If you wish to
+continue using the current hsql 1.8 database driver, no action is needed. When
+upgrading to a new version of Libresonic powered by liquibase you may see some
+liquibase logging to double check old migrations, but on subsequent startups it
+will not execute them again.
+
+For those that wish to change their database, instructions differ based on
+whether you wish for your database connection to be managed by your container (tomcat),
+or whether you wish Libresonic to manage it for you. The former may offer some performance 
+gains in the case of many concurrent users with connection pooling while the latter is easiest.
+
+We will refer to container managed configuration as jndi and libresonic managed configuration as embedded.
+
+## Embedded
+*Before doing anything, make sure your database is properly backed up. Ensure your server is shutdown*
+
+In your libresonic.properties file, you will need to add the following settings (this is just an example):
+
+```
+database.config.type=embed
+database.config.embed.driver=org.hsqldb.jdbcDriver
+database.config.embed.url=jdbc:hsqldb:file:/tmp/libre/db/libresonic
+database.config.embed.username=sa
+database.config.embed.password=
+```
+
+In addition, you will need to ensure that a jdbc driver suitable for your
+database is on the
+[classpath](https://docs.oracle.com/javase/8/docs/technotes/tools/windows/classpath.html)
+
+## JNDI
+*Before doing anything, make sure your database is properly backed up. Ensure your server is shutdown*
+
+In your libresonic.properties file, you will need to add the following settings (this is just an example):
+
+```
+database.config.type=jndi
+database.config.jndi.name=jdbc/libresonicDB
+```
+
+Then in your context.xml in your tomcat directory, add the jndi config:
+
+```
+    <Resource name="jdbc/libresonicDB" auth="Container"
+        type="javax.sql.DataSource"
+        maxActive="20"
+        maxIdle="30"
+        maxWait="10000"
+        username="libresonic"
+        password="REDACTED"
+        driverClassName="com.mysql.jdbc.Driver"
+        url="jdbc:mysql://hostname/libresonic?sessionVariables=sql_mode=ANSI_QUOTES"/>
+
+```
+
+Finally, copy the jdbc driver from the database vendor website to the `lib` directory in your tomcat folder.
+
+## Database Vendor Specific Notes
+
+### MySQL
+
+`sessionVariables=sql_mode=ANSI_QUOTES` on your jdbc url string may be necessary. TODO: double check this
+
+### PostgreSQL
+
+`stringtype=unspecified` on your jdbc url string is necessary.
+
+You will also need to add `database.usertable.quote=\"` to your properties
+file. This is due to the fact that our `user` table is a keyword for postgres.