AAP-36937: Added info. external database and variable behavior (#2688)

Author: sayjadha

downstream/modules/platform/proc-setup-postgresql-ext-database.adoc

@@ -4,8 +4,8 @@
 
 [IMPORTANT]
 ====
-Red{nbsp}Hat does not support the use of external (customer supported) databases, however they are used by customers. 
-The following guidance on initial configuration, from a product installation perspective only, is provided to avoid related support requests.
+* Red{nbsp}Hat does not support the use of external (customer supported) databases, however they are used by customers. The following guidance on initial configuration, from a product installation perspective only, is provided to avoid related support requests.
+* When using an external database with the {PlatformNameShort}, you must create and maintain that database. Ensure that you clear your external database when uninstalling the {PlatformNameShort}.
 ====  
 
 Use the following procedure to configure an external PostgreSQL compliant database for use with an {PlatformNameShort} component, for example {ControllerName}, {EDAName}, {HubName}, and {Gateway}.

downstream/modules/platform/ref-database-inventory-variables.adoc

@@ -44,7 +44,7 @@ PostgreSQL admin password.
 
 | | `postgresql_effective_cache_size` | PostgreSQL effective cache size.
 
-| | `postgresql_keep_databases` | Keep databases during uninstall.
+| | `postgresql_keep_databases` | Keep databases during uninstall. This variable applies to databases managed by the installer only, and not for external customer-created databases.
 
 Default = `false`