clarify slack notification method options (webhook vs api) in README

Author: yasunariw

README.md

@@ -33,10 +33,12 @@ Run the `_build/default/src/monorobot.exe` binary. The following commands are su
     2. [Create a webhook](https://docs.github.com/en/free-pro-team@latest/developers/webhooks-and-events/creating-webhooks#setting-up-a-webhook) for the repository you are targeting. Set the *Payload URL* to be `<server_domain>/github`.
     3. You can optionally [secure the webhook](https://docs.github.com/en/free-pro-team@latest/developers/webhooks-and-events/securing-your-webhooks) with a token, and store it in the `gh_hook_token` field of the secrets file.
 4. Configure Slack
-    1. [Create a Slack app](https://api.slack.com/apps?new_app=1). Click on "Basic Information" in the left sidebar, and update your secrets file with the `slack_client_id` and `slack_client_secret` with information from the page. You can optionally provide the `slack_signing_secret` to enforce [signature checking](https://api.slack.com/authentication/verifying-requests-from-slack) on incoming requests from Slack.
-    2. Click on "OAuth & Permissions" in the sidebar. Give your bot a *Bot Token Scope* of `chat:write`.
-    3. Click "Install to Workspace", and when prompted to grant permissions to your workspace, click "Allow".
-    4. Copy the generated OAuth access token (`xoxb-XXXX`) to the `slack_access_token` field of your secrets file. This token is used by the bot to authenticate to the workspace, and remains valid until the token is revoked or the app is uninstalled.
+    1. [Create a Slack app](https://api.slack.com/apps?new_app=1).
+    2. Click "Install to Workspace", and when prompted to grant permissions to your workspace, click "Allow".
+    3. Set up notifications with one of the following methods:
+        - **Web API (recommended):** To use Slack's [Web API](https://api.slack.com/web), click on "OAuth & Permissions" in your app dashboard's sidebar. Give your bot a *Bot Token Scope* of `chat:write`. Copy the generated OAuth access token (`xoxb-XXXX`) to the `slack_access_token` field of your secrets file. This token is used by the bot to authenticate to the workspace, and remains valid until the token is revoked or the app is uninstalled.
+        - **Incoming Webhooks:** To use [incoming webhooks](https://api.slack.com/messaging/webhooks), enable them in your app dashboard and create one for each channel you want to notify. Store them in the `slack_hooks` field of your secrets file. If you decide to notify additional channels later, you will need to update the secrets file with the new webhooks and restart the server.
+
 
 ### Documentation
 

documentation/secret_docs.md

@@ -41,10 +41,17 @@ Refer [here](https://api.slack.com/authentication/oauth-v2) for obtaining an acc
 Expected format:
 
 ```json
-{
-    "channel": "channel name",
-    "url": "webhook url"
-}
+[
+    {
+        "channel": "channel name",
+        "url": "webhook url"
+    },
+    {
+        "channel": "channel name",
+        "url": "webhook url"
+    },
+    ...
+]
 ```
 
 Refer [here](https://api.slack.com/messaging/webhooks) for obtaining a webhook for a channel.