Configuring a Read-Write LDAP User Store documentation for 3.1.0

Description:

When configuring Read-Write LDAP User Store for API Manager 3.1.0, if we add following configurations as mentioned in doc [1] server startup fails with following error:

WARN {org.wso2.config.mapper.ConfigParser} - Configurations Changed in :repository/conf/deployment.toml
[2020-03-16 17:28:38,568]  WARN {org.wso2.config.mapper.ConfigParser} - Overriding files in configuration directory /home/vithursa/Documents/APIManagementProject/rc-3.1.0/wso2am-3.1.0
[2020-03-16 17:28:38,839]  SEVERE {org.wso2.carbon.server.Main handleConfiguration} - Error while performing configuration changes 
org.wso2.config.mapper.ConfigParserException: Configuration with key user_store.base_dn doesn't exist
	at org.wso2.config.mapper.ReferenceResolver.resolvePropertyPlaceholders(ReferenceResolver.java:288)
	at org.wso2.config.mapper.ReferenceResolver.resolveConfigReferences(ReferenceResolver.java:124)
	at org.wso2.config.mapper.ReferenceResolver.resolve(ReferenceResolver.java:91)
	at org.wso2.config.mapper.ReferenceResolver.resolve(ReferenceResolver.java:71)
	at org.wso2.config.mapper.ConfigParser.parse(ConfigParser.java:253)
	at org.wso2.config.mapper.ConfigParser.deploy(ConfigParser.java:217)
	at org.wso2.config.mapper.ConfigParser.deployAndStoreMetadata(ConfigParser.java:180)
	at org.wso2.config.mapper.ConfigParser.parse(ConfigParser.java:127)
	at org.wso2.carbon.server.Main.handleConfiguration(Main.java:231)
	at org.wso2.carbon.server.Main.main(Main.java:103)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.wso2.carbon.bootstrap.Bootstrap.loadClass(Bootstrap.java:70)
	at org.wso2.carbon.bootstrap.Bootstrap.main(Bootstrap.java:51)

Following configurations should be added to make this work:

[user_store]
type = "read_write_ldap"
connection_url = "ldap://localhost:${Ports.EmbeddedLDAP.LDAPServerPort}"
connection_name = "uid=admin,ou=system"
connection_password = "admin"
base_dn = "dc=wso2,dc=org"

[1] https://apim.docs.wso2.com/en/latest/administer/product-administration/managing-users-and-roles/managing-user-stores/configure-primary-user-store/configuring-a-read-write-ldap-user-store/

Content Positioning in Documentation:

• Link: https://apim.docs.wso2.com/en/latest/administer/product-administration/managing-users-and-roles/managing-user-stores/configure-primary-user-store/configuring-a-read-write-ldap-user-store/