integration: define admin-tokens under identity-providers, as busbar 1.5.3 requires (#2)

Author: MattJackson

scripts/integration.sh

@@ -39,11 +39,14 @@ EOF
 cat > "$BUSBAR_CONFIG" <<EOF
 listen: "127.0.0.1:${PORT}"
 admin_listen: "127.0.0.1:${ADMIN_PORT}"
+# 1.5.3: inline module entries under `auth.admin_auth:` were retired. Each identity provider is
+# DEFINED once here and REFERENCED by bare name below; busbar refuses to boot the old inline shape.
+identity-providers:
+  admin-tokens: { module: admin-tokens, token: { env: BUSBAR_ADMIN_TOKEN } }
 auth:
   chain: [keys]
   signing_key: { file: "${WORK}/signing.key" }
-  admin_auth:
-    - admin-tokens: { token: { env: BUSBAR_ADMIN_TOKEN } }
+  admin_auth: [admin-tokens]
 providers:
   mock:
     api_key: { env: MOCK_KEY }