TechDocs/GCS: Update docs regarding credentials and removed projectId key

docs/features/techdocs/configuration.md

@@ -54,16 +54,15 @@ techdocs:
     # Required when techdocs.publisher.type is set to 'googleGcs'. Skip otherwise.
 
     googleGcs:
-      # An API key is required to write to a storage bucket.
+      # (Required) Cloud Storage Bucket Name
+      bucketName: 'techdocs-storage'
+
+      # (Optional) An API key is required to write to a storage bucket.
+      # If missing, GOOGLE_APPLICATION_CREDENTIALS environment variable will be used.
+      # https://cloud.google.com/docs/authentication/production
       credentials:
         $file: '/path/to/google_application_credentials.json'
 
-      # Your GCP Project ID where the Cloud Storage Bucket is hosted.
-      projectId: 'gcp-project-id'
-
-      # Cloud Storage Bucket Name
-      bucketName: 'techdocs-storage'
-
     # Required when techdocs.publisher.type is set to 'awsS3'. Skip otherwise.
 
     awsS3:

docs/features/techdocs/using-cloud-storage.md

@@ -30,20 +30,34 @@ techdocs:
     type: 'googleGcs'
 ```
 
-**2. GCP (Google Cloud Platform) Project**
+**2. GCS Bucket**
 
-Create or choose a dedicated GCP project. Set
-`techdocs.publisher.googleGcs.projectId` to the project ID.
+Create a dedicated Google Cloud Storage bucket for TechDocs sites.
+techdocs-backend will publish documentation to this bucket. TechDocs will fetch
+files from here to serve documentation in Backstage. Note that the bucket names
+are globally unique.
+
+Set the name of the bucket to `techdocs.publisher.googleGcs.bucketName`.
 
 ```yaml
 techdocs:
   publisher:
     type: 'googleGcs'
-  googleGcs:
-    projectId: 'gcp-project-id'
+    googleGcs:
+      bucketName: 'name-of-techdocs-storage-bucket'
 ```
 
-**3. Service account API key**
+**3a. (Recommended) Authentication using environment variable**
+
+The GCS Node.js client will automatically use the environment variable
+`GOOGLE_APPLICATION_CREDENTIALS` to authenticate with Google Cloud. It might
+already be set in Compute Engine, Google Kubernetes Engine, etc. Read
+https://cloud.google.com/docs/authentication/production for more details.
+
+**3b. Authentication using app-config.yaml**
+
+If you do not prefer (3a) and optionally like to use a service account, you can
+follow these steps.
 
 Create a new Service Account and a key associated with it. In roles of the
 service account, use "Storage Admin".
@@ -65,34 +79,29 @@ techdocs:
   publisher:
     type: 'googleGcs'
     googleGcs:
-      projectId: 'gcp-project-id'
+      bucketName: 'name-of-techdocs-storage-bucket'
       credentials:
         $file: '/path/to/google_application_credentials.json'
 ```
 
-**4. GCS Bucket**
-
-Create a dedicated bucket for TechDocs sites. techdocs-backend will publish
-documentation to this bucket. TechDocs will fetch files from here to serve
-documentation in Backstage.
-
-Set the name of the bucket to `techdocs.publisher.googleGcs.bucketName`.
+Note: If you are finding it difficult to make the file
+`google_application_credentials.json` available on a server, you could use the
+file's content and set as an environment variable. And then use
 
 ```yaml
 techdocs:
   publisher:
     type: 'googleGcs'
     googleGcs:
-      projectId: 'gcp-project-id'
-      credentials:
-        $file: '/path/to/google_application_credentials.json'
       bucketName: 'name-of-techdocs-storage-bucket'
+      credentials:
+        $env: TECHDOCS_GCS_CREDENTIALS
 ```
 
-**5. That's it!**
+**4. That's it!**
 
 Your Backstage app is now ready to use Google Cloud Storage for TechDocs, to
-store the static generated documentation files.
+store and read the static generated documentation files.
 
 ## Configuring AWS S3 Bucket with TechDocs
 
@@ -113,9 +122,8 @@ techdocs:
 **2. AWS Policies**
 
 AWS Policies lets you **control access** to Amazon Web Services (AWS) products
-and resources.  
-Here we will use a user policy **and** a bucket policy to show you the different
-possibilities you have but you can use only one.
+and resources. Here we will use a user policy **and** a bucket policy to show
+you the different possibilities you have but you can use only one.
 
 <img data-zoomable src="../../assets/techdocs/aws-s3.drawio.svg" alt="AWS S3" width="500" />
 
@@ -135,9 +143,9 @@ and the **user** policy.
 **2.1.1 Create an Admin user** (if you don't have one yet)
 
 Create an **administrator user** account `ADMIN_USER` and grant it administrator
-privileges by attaching a user policy giving the account **full access**.  
-Note down the Admin User credentials and IAM User Sign-In URL as you will need
-to use this information in the next step.
+privileges by attaching a user policy giving the account **full access**. Note
+down the Admin User credentials and IAM User Sign-In URL as you will need to use
+this information in the next step.
 
 **2.1.2 Create an AWS S3 Bucket**
 
@@ -171,9 +179,9 @@ In the IAM console, do the following:
 
 **2.2 Attach policies**
 
-Remember that you can use Bucket policy **or** User policy.  
-Just make sure that you grant all the permissions to the TechDocs user:
-`3:PutObject`, `s3:GetObject`, `s3:ListBucket` and `s3:GetBucketLocation`.
+Remember that you can use Bucket policy **or** User policy. Just make sure that
+you grant all the permissions to the TechDocs user: `3:PutObject`,
+`s3:GetObject`, `s3:ListBucket` and `s3:GetBucketLocation`.
 
 **2.2.1 Create the bucket policy**
 
@@ -209,9 +217,9 @@ section:
 - The first statement grants **TechDocs User** the bucket operation permissions
   `s3:GetBucketLocation` and `s3:ListBucket` which are permissions required by
   the console.
-- The second statement grants the `s3:GetObject` permission.  
-  (**NOTE :** if you do not use the user policy defined below you must also add
-  the `s3:PutObject` permission to allow the TechDocs user to add objects.)
+- The second statement grants the `s3:GetObject` permission. (**NOTE :** if you
+  do not use the user policy defined below you must also add the `s3:PutObject`
+  permission to allow the TechDocs user to add objects.)
 
 **2.2.2 Create the user policy**