feat(gcloud): Support publishing packages to GCP Artifact Registry (#47)

* feat(circleci): Publish packages to GCP repository

Author: caseydialpad

Diff for: gcloud/orb.yaml

@@ -135,6 +135,50 @@ commands:
             kubectl patch deployment <<parameters.deployment>> \
               -p '{"spec":{"template":{"metadata":{"annotations":{"date":"'$(date +'%s')'"}}}}}'
 
+  artifacts-package-publish:
+    description: >
+      This command will publish an already built package to a GCP package
+      repository. Command requires python3 to be present.
+    parameters:
+      creds:
+        default: GCLOUD_SERVICE_KEY
+        description: >
+          Name of environment variable storing the base64-encoded service key
+          for the GCP project.
+        type: env_var_name
+      files:
+        default: '*'
+        description: >
+          Glob pattern of files to upload
+        type: string
+      path:
+        default: .
+        description: >
+          Path to the directory containing your packages.
+        type: string
+      project:
+        description: >
+          Name of GCP project to which we will push.
+        type: string
+      repository-url:
+        description: >
+          URL of GCP package repository to which we will push.
+        type: string
+    steps:
+      - run: python3 -m pip install twine keyring keyrings.google-artifactregistry-auth
+      - install
+      - auth:
+          creds: <<parameters.creds>>
+          project: <<parameters.project>>
+      - run: |
+          unset TWINE_PASSWORD
+          unset TWINE_USERNAME
+          unset TWINE_REPOSITORY
+          unset TWINE_REPOSITORY_URL
+          unset TWINE_CERT
+          unset TWINE_NON_INTERACTIVE
+          twine upload --repository-url <<parameters.repository-url>> <<parameters.path>>/<<parameters.files>>
+
 jobs:
   deploy-cloud-function:
     description: >