Support MongoDB credential generation.

Fixes gh-28.

docs/src/main/asciidoc/README.adoc

@@ -7,8 +7,9 @@ include::intro.adoc[]
 
 Specifically for Spring applications:
 
-* Bind to the Config Server and initialize Spring `Environment` with remote property sources
+* Retrieve secrets from Vault and initialize Spring `Environment` with remote property sources
 * Obtain secrets secured with SSL
+* Generate credentials for MySQL, PostgreSQL, Apache Cassandra, MongoDB, Consul, AWS, and RabbitMQ.
 * https://www.vaultproject.io/docs/auth/token.html[Token], https://www.vaultproject.io/docs/auth/app-id.html[AppId] authentication,
 and https://www.vaultproject.io/docs/auth/aws-ec2.html[AWS-EC2] authentication
 * Bootstrap application context: a parent context for the main application that can be trained to do anything

docs/src/main/asciidoc/intro.adoc

@@ -1,2 +1,2 @@
 
-Spring Cloud Vault Config provides client-side support for externalized configuration in a distributed system. With https://www.vaultproject.io[Hashicorp's Vault] you have a central place to manage external secret properties for applications across all environments. Vault can manage static and dynamic secrets such as username/password for remote applications/resources and provide credentials for external services such as MySQL, PostgreSQL, Apache Cassandra, Consul, AWS and more.
+Spring Cloud Vault Config provides client-side support for externalized configuration in a distributed system. With https://www.vaultproject.io[Hashicorp's Vault] you have a central place to manage external secret properties for applications across all environments. Vault can manage static and dynamic secrets such as username/password for remote applications/resources and provide credentials for external services such as MySQL, PostgreSQL, Apache Cassandra, MongoDB, Consul, AWS and more.

docs/src/main/asciidoc/spring-cloud-vault-config.adoc

@@ -490,6 +490,7 @@ mechanism to more easily roll keys.
 Spring Cloud Vault integrates with these backends:
 
 * <<vault-client-database-cassandra>>
+* <<vault-client-database-mongodb>>
 * <<vault-client-database-mysql>>
 * <<vault-client-database-postgresql>>
 
@@ -547,6 +548,40 @@ spring.cloud.vault:
 
 See also: https://www.vaultproject.io/docs/secrets/cassandra/index.html[Vault Documentation: Setting up Apache Cassandra with Vault]
 
+[[vault-client-database-mongodb]]
+=== MongoDB
+
+Spring Cloud Vault can obtain credentials for MongoDB.
+The integration can be enabled by setting
+`spring.cloud.vault.mongodb.enabled=true` (default `false`) and
+providing the role name with `spring.cloud.vault.mongodb.role=…`.
+
+Username and password are stored in `spring.data.mongodb.username`
+and `spring.data.mongodb.password` so using Spring Boot will
+pick up the generated credentials without further configuration.
+You can configure the property names by setting
+`spring.cloud.vault.mongodb.username-property` and
+`spring.cloud.vault.mongodb.password-property`.
+
+[source,yaml]
+----
+spring.cloud.vault:
+    mongodb:
+        enabled: true
+        role: readonly
+        backend: mongodb
+        username-property: spring.data.mongodb.username
+        password-property: spring.data.mongodb.password
+----
+
+* `enabled` setting this value to `true` enables the MongodB backend config usage
+* `role` sets the role name of the MongoDB role definition
+* `backend` sets the path of the MongoDB mount to use
+* `username-property` sets the property name in which the MongoDB username is stored
+* `password-property` sets the property name in which the MongoDB password is stored
+
+See also: https://www.vaultproject.io/docs/secrets/mongodb/index.html[Vault Documentation: Setting up MongoDB with Vault]
+
 [[vault-client-database-mysql]]
 === MySQL