fix(clustered): document the use of special symbols PostgeSQL connection strings (#5591)

* fix(clustered): document the use of special symbols PostgeSQL connection strings

* docs: style fixup

Co-authored-by: Scott Anderson <sanderson@users.noreply.github.com>

* docs: style fixup

Co-authored-by: Scott Anderson <sanderson@users.noreply.github.com>

---------

Co-authored-by: Jason Stirnaman <jstirnaman@influxdata.com>
Co-authored-by: Scott Anderson <sanderson@users.noreply.github.com>

content/influxdb/clustered/install/configure-cluster/directly.md

@@ -544,9 +544,39 @@ We recommend storing sensitive credentials, such as your PostgreSQL-compatible D
 as secrets in your Kubernetes cluster.
 {{% /note %}}
 
-- `spec.package.spec.catalog.dsn.valueFrom.secretKeyRef`
-  - `.name`: Secret name
-  - `.key`: Key in the secret that contains the DSN
+{{% warn %}}
+#### Percent-encode special symbols in PostgreSQL DSNs
+
+Special symbols in PostgreSQL DSNs should be percent-encoded to ensure they
+are parsed correctly by InfluxDB Clustered. This is important to consider when
+using DSNs containing auto-generated passwords which may include special
+symbols to make passwords more secure.
+
+For example, the following DSN used in InfluxDB Clustered:
+
+```txt
+postgresql://postgres:meow#meow@my-fancy.cloud-database.party:5432/postgres
+```
+
+Would result in an error similar to:
+
+```txt
+Catalog DSN error: A catalog error occurred: unhandled external error: error with configuration: invalid port number
+```
+
+To fix this, percent-encode special symbols in the connection string:
+
+```txt
+postgresql://postgres:meow%23meow@my-fancy.cloud-database.party:5432/postgres
+```
+
+For more information, see the [PostgreSQL Connection URI
+docs](https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING-URIS).
+{{% /warn %}}
+
+- [ ] `spec.package.spec.catalog.dsn.valueFrom.secretKeyRef`
+  - [ ] `.name`: Secret name
+  - [ ] `.key`: Key in the secret that contains the DSN
 
 {{% code-placeholders "SECRET_(NAME|KEY)" %}}