Deprecate OgmPluginInitializer and document it.

CHANGES.txt

@@ -12,6 +12,7 @@ o Removed deprecated `org.neo4j.ogm.exception.core.NotFoundException`. (#319)
 o Removed deprecated `org.neo4j.ogm.exception.core.ResultErrorsException`. (#319)
 o Introduced exception translator to unify exceptions of different transports into an OGM hierarchy. (#319)
 o Improved hashing in IdentityMap and MappedRelationship. (#579)
+o Deprecated OgmPluginInitializer.
 
 3.1.x
 o Improve documentation of type conversions. #501

embedded-driver/src/main/java/org/neo4j/ogm/drivers/embedded/extension/OgmPluginInitializer.java

@@ -40,7 +40,13 @@
  *
  * @author Frantisek Hartman
  * @since 3.0
+ * @deprecated 3.2.0 this class implements the {@code PluginLifecycle} that is part of the Neo4j server plugins.
+ * Those plugins are also deprecated for removal in future releases.
+ * If you plan to use this in an unmanaged extension in the future, please create the Neo4j-OGM embedded driver manually
+ * within your extension.
+ *
  */
+@Deprecated
 public abstract class OgmPluginInitializer implements PluginLifecycle {
 
     protected final String packages;

neo4j-ogm-docs/src/main/asciidoc/reference/configuration.adoc

@@ -235,37 +235,8 @@ For Neo4j 3.4 those are `org.neo4j:neo4j-ha` and `org.neo4j:neo4j-enterprise`, f
 [[reference:configuration:driver:embedded:unmanaged]]
 ==== Configuration of an unmanaged extension
 
-When your application is running as unmanaged extension inside the Neo4j server itself, you will need to set up Neo4j-OGM configuration slightly differently.
-Neo4j provides `PluginLifecycle` SPI that allows to initialize extensions.
-Extend `OgmPluginInitializer` and list the full class name in `META-INF/services/org.neo4j.server.plugins.PluginLifecycle`:
-
-
-[source, java]
-----
-public class MyApplicationPluginInitializer extends OGMPluginInitializer {
-
-    public MyApplicationPluginInitializer() {
-        super(MyDomain.class.getPackage().getName());
-    }
-}
-----
-
-This provides `SessionFactory` as injectable in your resources:
-
-[source, java]
-----
-@Path("/movies")
-public static class MovieService {
-
-    @Context
-    private SessionFactory sessionFactory;
-
-    ...
-}
-----
-[NOTE]
-Don't forget to list your resources in `dbms.unmanaged_extension_classes` property in Neo4j configuration file as you
-would with any other unmanaged extension.
+The `OgmPluginInitializer` class was deprecated in Neo4j-OGM 3.2 and will be removed in the next major version.
+To use Neo4j-OGM within an unmanaged extension you connect to the database the usual way you would do with an embedded driver.
 
 
 [[reference:configuration:driver:credentials]]