declare the oauth2proxy clientSecret a secret

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

.changeset/late-turtles-sparkle.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-auth-backend': patch
+---
+
+Declare oauth2 `clientSecret` with visibility secret

plugins/auth-backend/config.d.ts

@@ -90,6 +90,9 @@ export interface Config {
       oauth2?: {
         [authEnv: string]: {
           clientId: string;
+          /**
+           * @visibility secret
+           */
           clientSecret: string;
           authorizationUrl: string;
           tokenUrl: string;