fix(postgres): tolerate databases declared without roles

`databases.<name>.roles` and its `admin`/`readonly` lists are optional in
the schema, but the init script dereferenced `$d.roles.admin` for every
database. A database declared with only `extensions`, or with an empty
body, failed the whole render with a nil pointer error instead of simply
granting nothing.

Treat a missing `roles`, `admin` or `readonly` as an empty list, so such a
database reconciles the same way as `roles: {}`: no grants, every managed
role revoked.

Assisted-by: LLM
Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

packages/apps/postgres/templates/init-script.yaml

@@ -204,13 +204,18 @@ stringData:
     echo "== assign roles to users"
     psql -v ON_ERROR_STOP=1 --echo-all <<\EOT
     {{- range $database, $d := .Values.databases }}
+    {{- /* roles, roles.admin and roles.readonly are all optional: a database
+         declared without them grants nothing and revokes every managed role. */}}
+    {{- $roles := default dict (default dict $d).roles }}
+    {{- $admin := default list $roles.admin }}
+    {{- $readonly := default list $roles.readonly }}
     {{- range $user, $u := $.Values.users }}
-    {{- if has $user $d.roles.admin }}
+    {{- if has $user $admin }}
     GRANT "{{ $database }}_admin" TO "{{ $user }}";
     {{- else }}
     REVOKE "{{ $database }}_admin" FROM "{{ $user }}";
     {{- end }}
-    {{- if has $user $d.roles.readonly }}
+    {{- if has $user $readonly }}
     GRANT "{{ $database }}_readonly" TO "{{ $user }}";
     {{- else }}
     REVOKE "{{ $database }}_readonly" FROM "{{ $user }}";

packages/apps/postgres/tests/database_roles_test.yaml

@@ -0,0 +1,97 @@
+suite: databases render without roles
+
+# `databases.<name>.roles`, `roles.admin` and `roles.readonly` are all optional
+# in the schema. The init script used to dereference `$d.roles.admin` for every
+# database, so a database declared with only `extensions` (or with nothing at
+# all) failed the whole render with "nil pointer evaluating interface {}.admin".
+# A missing list must read as an empty list: no user is granted the role, and
+# every managed role is revoked from every user, exactly as `roles: {}` does.
+
+templates:
+  - templates/init-script.yaml
+
+release:
+  name: pg-test
+  namespace: tenant-test
+
+set:
+  _cluster:
+    scheduling: {}
+  users:
+    app:
+      password: secret
+
+tests:
+  - it: "a database with only extensions renders and revokes both managed roles"
+    set:
+      databases:
+        events:
+          extensions:
+            - hstore
+    documentSelector:
+      path: metadata.name
+      value: pg-test-init-script
+    asserts:
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'REVOKE "events_admin" FROM "app";'
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'REVOKE "events_readonly" FROM "app";'
+      - notMatchRegex:
+          path: stringData["init.sh"]
+          pattern: 'GRANT "events_(admin|readonly)" TO'
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'CREATE EXTENSION IF NOT EXISTS hstore;'
+
+  - it: "a database with an empty body renders the same as roles: {}"
+    set:
+      databases:
+        events: {}
+    documentSelector:
+      path: metadata.name
+      value: pg-test-init-script
+    asserts:
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'REVOKE "events_admin" FROM "app";'
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'REVOKE "events_readonly" FROM "app";'
+
+  - it: "roles with only admin grants admin and revokes readonly"
+    set:
+      databases:
+        events:
+          roles:
+            admin:
+              - app
+    documentSelector:
+      path: metadata.name
+      value: pg-test-init-script
+    asserts:
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'GRANT "events_admin" TO "app";'
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'REVOKE "events_readonly" FROM "app";'
+
+  - it: "roles with only readonly grants readonly and revokes admin"
+    set:
+      databases:
+        events:
+          roles:
+            readonly:
+              - app
+    documentSelector:
+      path: metadata.name
+      value: pg-test-init-script
+    asserts:
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'REVOKE "events_admin" FROM "app";'
+      - matchRegex:
+          path: stringData["init.sh"]
+          pattern: 'GRANT "events_readonly" TO "app";'