DATACASS-4 - Add support for auditing.

We now support auditing using Spring's IsNewAwareAuditingHandler. Entities that are saved are processed before persisting these through auditing EntityCallbacks.

@Table
class Entity {

  @Id Long id;

  @CreatedDate
  LocalDateTime created;

  @LastModifiedDate
  LocalDateTime modified;

   // …
}

@EnableCassandraAuditing
@Configuration
class MyConfiguration extends AbstractReactiveCassandraConfiguration {

 // …
}

src/main/asciidoc/index.adoc

@@ -27,6 +27,8 @@ include::reference/converters.adoc[leveloffset=+1]
 include::reference/reactive-cassandra.adoc[leveloffset=+1]
 include::reference/cassandra-repositories.adoc[leveloffset=+1]
 include::reference/reactive-cassandra-repositories.adoc[leveloffset=+1]
+include::{spring-data-commons-docs}/auditing.adoc[leveloffset=+1]
+include::reference/cassandra-auditing.adoc[leveloffset=+1]
 include::reference/mapping.adoc[leveloffset=+1]
 
 [[appendix]]

src/main/asciidoc/new-features.adoc

@@ -11,6 +11,7 @@ This chapter summarizes changes and new features for each release.
 * Lightweight transaction support via `DeleteOptions` using the Template API.
 * Filter conditions for lightweight transaction update and delete (`UPDATE … IF <condition>`, `DELETE … IF <condition>`).
 * Optimistic Locking support.
+* Auditing via `@EnableCassandraAuditing`.
 
 [[new-features.2-1-0]]
 == What's new in Spring Data for Apache Cassandra 2.1

src/main/asciidoc/reference/cassandra-auditing.adoc

@@ -0,0 +1,33 @@
+[[cassandra.auditing]]
+== General Auditing Configuration for Cassandra
+
+To activate auditing functionality, add the Spring Data for Apache Cassandra `auditing` namespace element to your configuration, as the following example shows:
+
+.Activating auditing by using XML configuration
+====
+[source,xml]
+----
+<cassandra:auditing mapping-context-ref="customMappingContext" auditor-aware-ref="yourAuditorAwareImpl"/>
+----
+====
+
+Alternatively, auditing can be enabled by annotating a configuration class with the `@EnableCassandraAuditing` annotation, as the following example shows:
+
+.Activating auditing using JavaConfig
+====
+[source,java]
+----
+@Configuration
+@EnableCassandraAuditing
+class Config {
+
+  @Bean
+  public AuditorAware<AuditableUser> myAuditorProvider() {
+      return new AuditorAwareImpl();
+  }
+}
+----
+====
+
+If you expose a bean of type `AuditorAware` to the `ApplicationContext`, the auditing infrastructure picks it up automatically and uses it to determine the current user to be set on domain types.
+If you have multiple implementations registered in the `ApplicationContext`, you can select the one to be used by explicitly setting the `auditorAwareRef` attribute of `@EnableCassandraAuditing`.

src/main/asciidoc/reference/cassandra-entity-callbacks.adoc

@@ -0,0 +1,29 @@
+= Store specific EntityCallbacks
+
+Spring Data for Apache Cassandra uses the `EntityCallback` API for its auditing support and reacts on the following callbacks.
+
+.Supported Entity Callbacks
+[%header,cols="4"]
+|===
+| Callback
+| Method
+| Description
+| Order
+
+| Reactive/BeforeConvertCallback
+| onBeforeConvert(T entity, String collection)
+| Invoked before a domain object is converted to `org.bson.Document`.
+| `Ordered.LOWEST_PRECEDENCE`
+
+| Reactive/AuditingEntityCallback
+| onBeforeConvert(Object entity, String collection)
+| Marks an auditable entity _created_ or _modified_
+| 100
+
+| Reactive/BeforeSaveCallback
+| onBeforeSave(T entity, org.bson.Document target, String collection)
+| Invoked before a domain object is saved. +
+ Can modify the target, to be persisted, `Document` containing all mapped entity information.
+| `Ordered.LOWEST_PRECEDENCE`
+
+|===

src/main/asciidoc/reference/mapping.adoc

@@ -655,3 +655,6 @@ The `AbstractCassandraEventListener` has the following callback methods:
 * `onAfterConvert`: Called in the `CassandraTemplate.select(…)`, `.slice(…)`, and `.stream(…)` methods after converting a row retrieved from the database to a POJO.
 
 NOTE: Lifecycle events are emitted only for root-level types. Complex types used as properties within an aggregate root are not subject to event publication.
+
+include::../{spring-data-commons-docs}/entity-callbacks.adoc[leveloffset=+1]
+include::./cassandra-entity-callbacks.adoc[leveloffset=+2]