Create PostgreSQL Secret even if postgresql.enabled=false

Ensures that the PostgreSQL Secret is created, even if
`postgresql.enabled=false`. This ensures that we support a use case
where folks want to use an external instance of PostgreSQL, but still
want the Secret to automatically be generated with the proper connection
string.

With a recent change, we would skip creation of this secret if
PostgreSQL was disabled which forced users to create a Secret
themselves. This change now allows them to continue providing the `auth`
values and letting the chart build the Secret with the correct
connection string.

Closes #358

charts/prefect-server/README.md

@@ -45,9 +45,15 @@ prefect-server:
   postgresql:
     # Disable the objects from the bundled PostgreSQL chart
     enabled: false
+
     auth:
-      # Provide the name of an existing secret following the instructions above.
+      # Option 1: provide the name of an existing secret following the instructions above.
       existingSecret: <existing secret name>
+
+      # Option 2: provide the connection string details directly
+      username: myuser
+      password: mypass
+      database: mydb
 ```
 
 Two secrets are created when not providing an existing secret name:

charts/prefect-server/README.md.gotmpl

@@ -44,9 +44,15 @@ prefect-server:
   postgresql:
     # Disable the objects from the bundled PostgreSQL chart
     enabled: false
+
     auth:
-      # Provide the name of an existing secret following the instructions above.
+      # Option 1: provide the name of an existing secret following the instructions above.
       existingSecret: <existing secret name>
+
+      # Option 2: provide the connection string details directly
+      username: myuser
+      password: mypass
+      database: mydb
 ```
 
 Two secrets are created when not providing an existing secret name:

charts/prefect-server/templates/secret.yaml

@@ -1,4 +1,4 @@
-{{- if and .Values.postgresql.enabled (not .Values.postgresql.auth.existingSecret) }}
+{{- if not .Values.postgresql.auth.existingSecret }}
 apiVersion: v1
 kind: Secret
 metadata: