[Server] backporting DOCSP-11308 to v4.0

Author: steveren

source/index.txt

@@ -34,6 +34,11 @@ database:
   features such as LDAP and Kerberos support, on-disk encryption, 
   and auditing.
 
+MongoDB also offers
+`Atlas <https://www.mongodb.com/cloud/atlas?jmp=docs_server>`__,
+a hosted MongoDB Enterprise service option in the cloud which requires
+no installation overhead and offers a free tier to get started.
+
 The Manual documents both MongoDB Community and Enterprise features and
 functionality.