Add Google Tasks integration documentation (#29498)

* Add Google Tasks integration documentation

* Tiny tweaks

---------

Co-authored-by: c0ffeeca7 <38767475+c0ffeeca7@users.noreply.github.com>

source/_integrations/google_tasks.markdown

@@ -0,0 +1,73 @@
+---
+title: Google Tasks
+description: Instructions on how to use Google Tasks in Home Assistant.
+ha_category:
+  - To-do List
+ha_iot_class: Cloud Polling
+ha_release: 2023.11
+ha_config_flow: true
+ha_domain: google_tasks
+ha_platforms:
+  - todo
+ha_codeowners:
+  - '@allenporter'
+ha_integration_type: integration
+---
+
+The **Google Tasks** integration allows you to connect your [Google Tasks](https://support.google.com/tasks/answer/7675772) to Home Assistant. The integration adds a [to-do list entity](/integrations/todo) for
+each task list, allowing you to create, update, or delete items on the list from the **To-do list** dashboard.
+
+## Prerequisites
+
+You need to configure developer credentials to allow Home Assistant to access your Google Account.
+These credentials are the same as the ones for [Nest](/integrations/nest) and [Google Mail](/integrations/google_mail).
+These are not the same as the one for [Google Calendar](/integrations/google).
+If you have already set up the correct credentials, you can do step 1 and then skip to step 13 on the below instructions.
+
+{% details "Generate Client ID and Client Secret" %}
+
+This section explains how to generate a Client ID and Client Secret on
+[Google Developers Console](https://console.cloud.google.com/apis/library/tasks.googleapis.com).
+
+1. First, go to the Google Developers Console to enable [Google Tasks](https://console.cloud.google.com/apis/library/tasks.googleapis.com)
+2. The wizard will ask you to choose a project to manage your application. Select a project and select **Continue**.
+3. Verify that your Google Tasks API was enabled and select **Go to credentials**.
+4. Navigate to **APIs & Services** (left sidebar) > [Credentials](https://console.cloud.google.com/apis/credentials).
+5. Click on the field on the left of the screen, **OAuth Consent Screen**.
+6. Select **External** and **Create**.
+7. Set the **App Name** (the name of the application asking for consent) to anything you want, for example to *Home Assistant*.
+8. You then need to select a **Support email**. To do this, from the dropdown menu, select your email address.
+9. You finally need to complete the section: **Developer contact information**. To do this, enter your email address (the same as above is fine).
+10. Scroll to the bottom and select **Save and Continue**. You don't have to fill out anything else, or it may enable additional review.
+11. You will then be automatically taken to the **Scopes** page. You do not need to add any scopes here, so select **Save and Continue** to move to the **Optional info** page. You do not need to add anything to the **Optional info** page, so select **Save and Continue**, which will take you to the **Summary** page. Select **Back to Dashboard**.
+12. Select **OAuth consent screen** again and set **Publish Status** to **Production**. Otherwise, your credentials will expire every 7 days.
+13. Make sure **Publishing status** is set to production.
+14. Select **Credentials** in the menu on the left-hand side of the screen, then select **Create credentials** (at the top of the screen), then select **OAuth client ID**.
+15. Set the Application type to **Web application** and give this credential set a name (like "Home Assistant Credentials").
+16. Add `https://my.home-assistant.io/redirect/oauth` to **Authorized redirect URIs** then select **Create**. This is not a placeholder and is the URI that must be used.
+17. You will then be presented with a pop-up saying **OAuth client created**, showing **Your Client ID** and **Your Client Secret**. Make a note of these (for example, copy and paste them into a text editor), as you will need them shortly. Once you have noted these strings, select **OK**. If you need to find these credentials again at any point, then navigate to **APIs & Services** > **Credentials**, and you will see **Home Assistant Credentials** (or whatever you named them in the previous step) under **OAuth 2.0 Client IDs**. To view both the **Client ID** and **Client secret**, select the pencil icon. This will take you to the settings page for these credentials, and the information will be on the right-hand side of the page.
+18. Double-check that the **Google Tasks API** has been automatically enabled. To do this, select **Library** from the menu, then search for **Google Tasks API**. If it is enabled, you will see **API Enabled** with a green tick next to it. If it is not enabled, then enable it.
+
+{% enddetails %}
+
+{% include integrations/config_flow.md %}
+
+The integration setup will next give you instructions to enter the [Application Credentials](/integrations/application_credentials/) (OAuth Client ID and Client Secret) and authorize Home Assistant to access your Google Tasks.
+
+{% details "OAuth and Device Authorization steps" %}
+
+1. Continue through the steps of selecting the account you want to authorize.
+
+2. **NOTE**: You may get a message telling you that the app has not been verified and you will need to acknowledge that in order to proceed.
+
+3. You can now see the details of what you are authorizing Home Assistant to access with two options at the bottom. Select **Continue**.
+
+4. The page will now display **Link account to Home Assistant?**, note **Your instance URL**. If this is not correct, refer to [My Home Assistant](/integrations/my). If everything looks good, select **Link Account**.
+
+5. You may close the window, and return back to Home Assistant where you should see a **Success!** message from Home Assistant.
+
+{% enddetails %}
+
+## Troubleshooting
+
+If you have an error with your credentials, you can delete them in the [Application Credentials](/integrations/application_credentials/) user interface.