Update/clarify docs on generic backend ttl.

Ping #2697

website/source/api/secret/generic/index.html.md

@@ -51,6 +51,12 @@ $ curl \
 }
 ```
 
+_Note_: the `lease_duration` field (which on the CLI shows as
+`refresh_interval`) is advisory. No lease is created. This is a way for writers
+to indicate how often a given value shold be re-read by the client. See the
+[Vault Generic backend documentation](/docs/secrets/generic/index.html) for
+more details.
+
 ## List Secrets
 
 This endpoint returns a list of key names at the specified location. Folders are
@@ -114,8 +120,9 @@ policy granting the `update` capability.
 
 - `:key` `(string: "")` – Specifies a key, paired with an associated value, to
   be held at the given location. Multiple key/value pairs can be specified, and
-  all will be returned on a read operation. A key called `ttl` will trigger some
-  special behavior; see above for details.
+  all will be returned on a read operation. A key called `ttl` will trigger
+  some special behavior; see the [Vault Generic backend
+  documentation](/docs/secrets/generic/index.html) for details.
 
 ### Sample Payload
 

website/source/docs/secrets/generic/index.html.md

@@ -42,6 +42,8 @@ normal `lease_duration`. However, the given value will also still be returned
 exactly as specified, so you are free to use that key in any way that you like
 if it fits your input data.
 
+The backend _never_ removes data on its own; the `ttl` key is merely advisory.
+
 As an example, we can write a new key "foo" to the generic backend mounted at
 "secret/" by default: