[discourse-gatekeeper] Migrate charm docs

docs/how-to/h-set-up/h-scale.md

@@ -17,24 +17,27 @@ To deploy PostgreSQL with multiple replicas, specify the number of desired units
 juju deploy postgresql --channel 14/stable -n <number_of_replicas>
 ```
 
-To retrieve the primary replica, one can use the action `get-primary` on any of the units running ` postgresql`:
+### Primary vs. leader unit
+
+The [PostgreSQL primary server](https://www.postgresql.org/docs/current/runtime-config-replication.html#RUNTIME-CONFIG-REPLICATION-PRIMARY) unit may or may not be the same as the [juju leader unit](https://juju.is/docs/juju/leader). 
+
+The juju leader unit is the represented in `juju status` by an asterisk (*) next to its name. 
+
+To retrieve the juju unit that corresponds to the PostgreSQL primary, use the action `get-primary` on any of the units running ` postgresql`:
 ```shell
 juju run postgresql/leader get-primary
 ```
-
 Similarly, the primary replica is displayed as a status message in `juju status`. However, one should note that this hook gets called on regular time intervals and the primary may be outdated if the status hook has not been called recently. 
 
-### `update-status` hook
-
-**We highly suggest configuring the status hook to run frequently.** In addition to reporting the primary, secondaries, and other statuses, the status hook performs self-healing in the case of a network cut. 
+[note]
+**We highly suggest configuring the `update-status` hook to run frequently.** In addition to reporting the primary, secondaries, and other statuses, the [status hook](https://juju.is/docs/sdk/update-status-event) performs self-healing in the case of a network cut. 
 
 To change the frequency of the `update-status` hook, run
 ```shell
 juju model-config update-status-hook-interval=<time(s/m/h)>
 ```
-Note that this hook executes a read query to PostgreSQL. On a production level server, this should be configured to occur at a frequency that doesn't overload the server with read requests. Similarly, the hook should not be configured at too quick of a frequency, as this can delay other hooks from running. 
-
-You can read more about status hooks [here](https://juju.is/docs/sdk/update-status-event).
+<!--Note that this hook executes a read query to PostgreSQL. On a production level server, this should be configured to occur at a frequency that doesn't overload the server with read requests. Similarly, the hook should not be configured at too quick of a frequency, as this can delay other hooks from running. -->
+[/note]
 
 ## Scale replicas on an existing application