fix(shorebird_code_push_api): secrets access (#18)

packages/shorebird_code_push_api/bin/server.dart

@@ -16,16 +16,15 @@ Future<void> main() async {
     ..post('/api/v1/releases', uploadReleaseHandler)
     ..get('/api/v1/engines/<revision>', downloadEngineHandler);
 
-  final apiKeys = json.decode(
-    Platform.environment['CODE_PUSH_API_KEYS'] ?? '[]',
-  ) as List;
-
-  final gcpKey = Platform.environment['GCP_SA'] ?? '';
+  final gcpKey = Platform.environment['GCP_SA']!;
+  final apiKeys =
+      (json.decode(Platform.environment['CODE_PUSH_API_KEYS']!) as List)
+          .cast<String>();
 
   final handler = const Pipeline()
       .addMiddleware(versionStoreProvider)
       .addMiddleware(httpClientProvider(gcpKey))
-      .addMiddleware(apiKeyVerifier(keys: apiKeys.cast<String>()))
+      .addMiddleware(apiKeyVerifier(apiKeys))
       .addHandler(router.call);
 
   final server = await shelf_io.serve(

packages/shorebird_code_push_api/lib/src/middleware/api_key_verifier.dart

@@ -2,7 +2,7 @@ import 'dart:io';
 
 import 'package:shelf/shelf.dart';
 
-Middleware apiKeyVerifier({List<String> keys = const []}) {
+Middleware apiKeyVerifier([List<String> keys = const []]) {
   return (handler) {
     return (request) async {
       final apiKey = request.headers['x-api-key'];

packages/shorebird_code_push_api/test/src/middleware/api_key_verifier_test.dart

@@ -20,7 +20,7 @@ void main() {
 
     test('returns 401 if key is invalid', () async {
       final handler = const Pipeline()
-          .addMiddleware(apiKeyVerifier(keys: keys))
+          .addMiddleware(apiKeyVerifier(keys))
           .addHandler((_) => Response.ok('OK'));
 
       final request = Request(
@@ -34,7 +34,7 @@ void main() {
 
     test('returns 200 if key is valid', () async {
       final handler = const Pipeline()
-          .addMiddleware(apiKeyVerifier(keys: keys))
+          .addMiddleware(apiKeyVerifier(keys))
           .addHandler((_) => Response.ok('OK'));
 
       final request = Request(