DATAMONGO-1968 - Add configuration support for com.mongodb.client.MongoClient.

We now accept MongoDB's new com.mongodb.client.MongoClient object to setup Spring Data MongoDB infrastructure through AbstractMongoClientConfiguration. The new MongoClient does not support DBObject anymore hence it cannot be used with Querydsl.

@Configuration
public class MongoClientConfiguration extends AbstractMongoClientConfiguration {

	@Override
	protected String getDatabaseName() {
		return "database";
	}

	@Override
	public MongoClient mongoClient() {
		return MongoClients.create("mongodb://localhost:27017/?replicaSet=rs0&w=majority");
	}
}

Original pull request: #557.

src/main/asciidoc/reference/mongodb.adoc

@@ -366,6 +366,28 @@ NOTE: Username/password credentials used in XML configuration must be URL encode
 Example: `m0ng0@dmin:mo_res:bw6},Qsdxx@admin@database` -> `m0ng0%40dmin:mo_res%3Abw6%7D%2CQsdxx%40admin@database`
 See https://tools.ietf.org/html/rfc3986#section-2.2[section 2.2 of RFC 3986] for further details.
 
+As of MongoDB java driver 3.7.0 there is an alternative entry point to `MongoClient` via the http://search.maven
+.org/#search%7Cgav%7C1%7Cg%3A%22org.mongodb%22%20AND%20a%3A%22mongodb-driver-sync%22[mongodb-driver-sync] artifact.
+`com.mongodb.client.MongoClient` is *not* compatible with `com.mongodb.MongoClient` and does not longer support
+the legacy `DBObject` codec. Therefore it cannot be used with `Querydsl` and requires a different configuration.
+You may use `AbstractMongoClientConfiguration` to leverage the new `MongoClients` builder API.
+
+[source,java]
+----
+@Configuration
+public class MongoClientConfiguration extends AbstractMongoClientConfiguration {
+
+	@Override
+	protected String getDatabaseName() {
+		return "database";
+	}
+
+	@Override
+	public MongoClient mongoClient() {
+		return MongoClients.create("mongodb://localhost:27017/?replicaSet=rs0&w=majority");
+	}
+}
+----
 
 [[mongo.mongo-db-factory-xml]]
 === Registering a MongoDbFactory instance using XML based metadata