fix: default pg connection config:check type

Signed-off-by: Sandor Karpf <sandor.karpf@lastpass.com>

.changeset/pretty-days-taste.md

@@ -0,0 +1,7 @@
+---
+'@backstage/backend-defaults': patch
+---
+
+Fixed `yarn backstage-cli config:check --strict --config app-config.yaml` config validation error by adding
+an optional `default` type discriminator to PostgreSQL connection configuration,
+allowing `config:check` to properly validate `default` connection configurations.

packages/backend-defaults/config.d.ts

@@ -633,6 +633,10 @@ export interface Config {
             ipAddressType?: 'PUBLIC' | 'PRIVATE' | 'PSC';
           }
         | {
+            /**
+             * The rest config for default, regular connections
+             */
+            type?: 'default';
             /**
              * Password that belongs to the client User
              * @visibility secret