Document how to add IAG adapter

Author: steven-schattenberg-itential

docs/iap_guide.md

@@ -12,6 +12,8 @@ The playbook and roles in this section install and configure IAP for the Itentia
 
 The `platform` role performs a base install of IAP including any OS packages required. It includes the appropriate version of Python, Pip, Jinja, and TextFSM. It handles a few security vulnerabilities. It creates the appropriate Linux users, directories, log files, and systemd services. It will start the automation-platform service when complete.
 
+When there is a device configured in the `gateway` group this role will also install and configure an IAG adapter that points to the gateway server named in the `gateway` group.
+
 ## Platform Adapters Role
 
 The `platform_adapters` role will install the source code for each adapter that is listed.  It will also install any listed custom adapters.  It can install from a Git URL or using an adapter archive generated by Adapter Builder.  It will restart the automation-platform service when complete.
@@ -118,7 +120,7 @@ The following table lists the default variables located in `roles/platform_app_a
 
 # Building the Inventory
 
-To install and configure IAP, add a `platform` group and host(s) to your inventory and configure the `iap_release` and either `iap_bin_file`, `iap_tar_file`, or `iap_archive_download_url`. The `iap_archive_download_url` supports Sonatype Nexus and JFrog Artifactory. It is recommended to use `repository_username` and `repository_password` for Nexus and `repository_api_key` for Artifactory.  The following inventory shows a basic IAP configuration with a single IAP node. 
+To install and configure IAP, add a `platform` group and host(s) to your inventory and configure the `iap_release` and either `iap_bin_file`, `iap_tar_file`, or `iap_archive_download_url`. The `iap_archive_download_url` supports Sonatype Nexus and JFrog Artifactory. It is recommended to use `repository_username` and `repository_password` for Nexus and `repository_api_key` for Artifactory.  The following inventory shows a basic IAP configuration with a single IAP node.
 
 ## Example Inventory - Single IAP Node