Update Pub/Sub Emulator

1. Update Local Emulator
   Run the following command to make sure you have the latest version of the pubsub emulator installed via gcloud:

   gcloud components update pubsub-emulator

2. Locate Emulator Directory
   The emulator represents a directory likely located at <gcloud-install-path>/platform/pubsub-emulator.
   You can find the exact path by running the emulator and checking the output, or by inspecting where gcloud is installed (e.g. which gcloud usually points to a bin directory, and the platform directory is a sibling of bin).
   Verify the version by running the emulator or checking the VERSION file if it exists.

3. Package the Emulator
   Zip the directory found in the previous step. Name it pubsub-emulator-<version>.zip.
   Ensure the zip structure is such that the top-level directory inside the zip is pubsub-emulator.
   Note: The existing code expects the binary at pubsub-emulator-<version>/pubsub-emulator/bin/cloud-pubsub-emulator inside the cache, which usually means the zip contains a root folder pubsub-emulator.

4. Upload to Storage
   Upload the zip file to the Firebase preview bucket:

   gsutil cp pubsub-emulator-<version>.zip gs://firebase-preview-drop/emulator/

   Make the file publicly readable if necessary (usually the bucket permissions handle this, or use gsutil acl ch -u AllUsers:R ...).

   Note: For the version 0.8.27 update, this step was already done.

5. Calculate Metadata
   Calculate the file size in bytes, MD5 checksum, and SHA256 checksum of the zip file.

   # Size
   ls -l pubsub-emulator-<version>.zip
   
   # MD5 (macOS: `md5`, Linux: `md5sum`)
   md5 pubsub-emulator-<version>.zip
   
   # SHA256 (macOS: `shasum -a 256`, Linux: `sha256sum`)
   shasum -a 256 pubsub-emulator-<version>.zip

6. Update Configuration
   Edit src/emulator/downloadableEmulatorInfo.json:

   • Update pubsub.version to the new version.
   • Update pubsub.expectedSize.
   • Update pubsub.expectedChecksum (MD5).
   • Update pubsub.expectedChecksumSHA256.
   • Update pubsub.remoteUrl and pubsub.downloadPathRelativeToCacheDir.

7. Verify
   Run the emulators to ensure the new version is downloaded and starts correctly.

   firebase emulators:start --only pubsub

8. Add a Changelog Entry
   Add a changelog entry to CHANGELOG.md like '- Updated Pub/Sub emulator to version '