docs: add instructions for authenticating for system tests (#398)

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Synth log will be available here:
https://source.cloud.google.com/results/invocations/f858a143-daac-4e50-b9ae-219abe9981ce/targets

- [ ] To automatically regenerate this PR, check this box.

Source-Link: googleapis/synthtool@363fe30

CONTRIBUTING.md

@@ -37,6 +37,13 @@ accept your pull requests.
 1.  Title your pull request following [Conventional Commits](https://www.conventionalcommits.org/) styling.
 1.  Submit a pull request.
 
+### Before you begin
+
+1.  [Select or create a Cloud Platform project][projects]. 
+1.  [Set up authentication with a service account][auth] so you can access the
+    API from your local workstation.
+
+
 ## Running the tests
 
 1.  [Prepare your environment for Node.js setup][setup].
@@ -51,15 +58,17 @@ accept your pull requests.
         npm test
 
         # Run sample integration tests.
-        gcloud auth application-default login
         npm run samples-test
 
         # Run all system tests.
-        gcloud auth application-default login
         npm run system-test
 
 1.  Lint (and maybe fix) any changes:
 
         npm run fix
 
 [setup]: https://cloud.google.com/nodejs/docs/setup
+[projects]: https://console.cloud.google.com/project
+[billing]: https://support.google.com/cloud/answer/6293499#enable-billing
+
+[auth]: https://cloud.google.com/docs/authentication/getting-started

synth.metadata

@@ -4,65 +4,15 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/gcs-resumable-upload.git",
-        "sha": "c35be0daa975edf0696f0724d50100c60313d10d"
+        "sha": "e76fe4a9b2809c9cc87f5ea1ad0af9ed26885ecc"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "ba9918cd22874245b55734f57470c719b577e591"
+        "sha": "363fe305e9ce34a6cd53951c6ee5f997094b54ee"
       }
     }
-  ],
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-    ".github/ISSUE_TEMPLATE/support_request.md",
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 }