Add plugin details to host catalog, host set, and host domain model pages (#1715)

* Add plugin information to host catalogs, host sets, and hosts.

website/content/docs/concepts/domain-model/host-catalogs.mdx

@@ -20,6 +20,19 @@ A host catalog has the following configurable attributes:
 
 - `description` - (optional)
 
+### Plugin Host Catalog Information and Attributes
+
+- `plugin_id` - (required)
+  Must reference an installed plugin.
+
+- `attributes` - (optional)
+  A collection of fields which the plugin uses to interface with the backing
+  service.
+
+- `secrets` - (optional)
+  A collection of sensitive fields, like credentials, which the plugin uses to
+  interface with the backing service.  These fields are write-only.
+
 ## Referenced By
 
 - [Host][]

website/content/docs/concepts/domain-model/host-sets.mdx

@@ -25,6 +25,23 @@ A host set has the following configurable attributes:
 
 - `description` - (optional)
 
+- `preferred_endpoints` - (optional)
+  A list of selector strings in the format of either `cidr:<valid IPv4/6 CIDR>`
+  or `dns:<globbed name>` used to select the addresses of [hosts][] when
+  establishing a [session][] with a [target][].
+
+### Plugin Host Set Attributes
+
+- `attributes` - (optional)
+  A collection of fields which the plugin uses to lookup which hosts should be
+  members of this host set.  Often this includes a type of filter using a
+  syntax which is usable by the backing service.
+
+- `sync_interval_seconds` - (optional)
+  The number of seconds between the time boundary syncs the [hosts][] in this
+  set using this host set's plugin. If not provided a system determined default
+  is used.
+
 ## Referenced By
 
 - [Host][]
@@ -37,6 +54,8 @@ A host set has the following configurable attributes:
 [hosts]: /docs/concepts/domain-model/hosts
 [project]: /docs/concepts/domain-model/scopes#projects
 [projects]: /docs/concepts/domain-model/scopes#projects
+[session]: /docs/concepts/domain-model/sessions
+[sessions]: /docs/concepts/domain-model/sessions
 [target]: /docs/concepts/domain-model/targets
 [targets]: /docs/concepts/domain-model/targets
 

website/content/docs/concepts/domain-model/hosts.mdx

@@ -14,6 +14,13 @@ A host belongs to a [host catalog][].
 Hosts can only be associated with [host sets][]
 from the same host catalog as the host.
 
+## Plugin Based Host Information
+
+Plugin based hosts are read-only.  They are synced by an installed plugin on
+the boundary system using the configuration provided it from the
+[host catalog][] and [host set][] at an interval (configurable in the
+[host set][]).
+
 ## Attributes
 
 A host has the following configurable attributes:

website/content/docs/concepts/domain-model/sessions.mdx

@@ -64,6 +64,8 @@ Changes to a user's permissions do not effect existing sessions.
 
 - [Project][]
 - [Credential][]
+- [Host Set][]
+- [Target][]
 
 [expiration time]: /docs/concepts/domain-model/targets#session_max_seconds
 [connection limit]: /docs/concepts/domain-model/targets#session_connection_limit