Google pubsub (#8153)

* Add basic documentation for google_pubsub

* Add guide to saving data

* Fix markdown

* 📝 Tweaks

* Make configuration quick-start proof.

* ✏️ Tweaks

* Bump release version to 0.87

* Bump release

* Update category to History

source/_components/google_pubsub.markdown

@@ -0,0 +1,86 @@
+---
+layout: page
+title: "Google Pub/Sub"
+description: "Setup for Google Pub/Sub integration"
+date: 2019-01-12 13:30
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: google-pubsub.png
+ha_category: History
+ha_release: 0.88
+---
+
+The `google_pubsub` component allows you to hook into the Home Assistant event bus and send events to [Google Cloud Pub/Sub](https://cloud.google.com/pubsub/docs/overview). The current [free tier](https://cloud.google.com/free/) of GCP should allow you to sync about 1 event every 2 seconds on average (2 million invocations per month).
+
+## {% linkable_title First time setup %}
+
+This assumes you already have a Google Cloud project. If you don't, please create one in the [Google Cloud Console](https://console.cloud.google.com/projectcreate)
+
+You need to create a Service Account key in the [Google Cloud API Console](https://console.cloud.google.com/apis/credentials/serviceaccountkey)
+- Choose a new "New Service Account", give it a name and leave the key type as JSON
+- Select the role: Pub/Sub Publisher 
+
+This will download the Service Account JSON key to your machine. Do NOT share this with anyone. Place this file in your Home Assistant config folder.
+
+Next, create a Google Pub/Sub topic in the [Google Cloud API Console](https://console.cloud.google.com/cloudpubsub/topicList). The topic name will become something like `projects/project-198373/topics/topic-name`. Note the last part only (the name you chose): `topic-name`.
+
+
+## {% linkable_title Configuration %}
+
+Add the following lines to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+google_pubsub:
+  project_id: YOUR_PROJECT_ID
+  topic_name: YOUR_TOPIC_NAME
+  credentials_json: CREDENTIALS_FILENAME
+```
+
+{% configuration %}
+project_id:
+  description: Project ID from the Google console (looks like `words-2ab12`).
+  required: true
+  type: string
+topic_name:
+  description: The Pub/Sub topic name.
+  required: true
+  type: string
+credentials_json:
+  description: The filename of the Google Service Account JSON file.
+  required: true
+  type: string
+filter:
+  description: Filter domains and entities for Google Cloud Pub/Sub.
+  required: false
+  type: map
+  default: Includes all entities from all domains
+  keys:
+    include_domains:
+      description: List of domains to include (e.g., `light`).
+      required: false
+      type: list
+    exclude_domains:
+      description: List of domains to exclude (e.g., `light`).
+      required: false
+      type: list
+    include_entities:
+      description: List of entities to include (e.g., `light.attic`).
+      required: false
+      type: list
+    exclude_entities:
+      description: List of entities to include (e.g., `light.attic`).
+      required: false
+      type: list
+{% endconfiguration %}
+
+<p class='note warning'>
+  Not filtering domains or entities will send every event to Google PubSub, thus hitting the free tier limit very fast. Be sure to fill in this configuration parameter or have a paid subscription for Google Cloud.
+</p>
+
+### {% linkable_title Saving the data using a Google Cloud Function %}
+
+To save your data automatically to BigQuery, follow the [instructions here](https://github.com/timvancann/home-assistant-pubsub-cloud-function). The current [free tier](https://cloud.google.com/free/) of GCP should allow to store up to 10GB of data.
+