slack bridge: Update doc for current version of making Slack bot user.
@@ -15,9 +15,19 @@ This is a bridge between Slack and Zulip.
### 2. Slack endpoint
1. Make sure Websocket isn't blocked in the computer where you run this bridge.
Test it at https://www.websocket.org/echo.html.
-2. Go to https://api.slack.com/apps?new_classic_app=1 and create a new classic app (note: must be a classic app). Choose a bot name that will be put into bridge_with_slack_config.py, e.g. "zulip_mirror". Make sure to install the app to the workspace. When successful, you should see a token that starts with "xoxb-..." (there is also a token that starts with "xoxp-...", we need the "xoxb-..." one).
-3. (Important) Make sure the bot is subscribed to the channel. You can do this by typing e.g. `/invite @zulip_mirror` in the relevant channel.
-4. In the `slack` section of the configuration file, enter the bot name (e.g. "zulip_mirror") and token, and the channel ID (note: must be ID, not name).
+2. Go to https://api.slack.com/apps?new_classic_app=1 and create a new classic
+ app (note: must be a classic app). Choose a bot name that will be put into
+ bridge_with_slack_config.py, e.g. "zulip_mirror". In the process of doing
+ this, you need to add oauth token scope. Simply choose `bot`. Slack will say
+ that this is a legacy scope, but we still need to use it anyway. The reason
+ why we need the legacy scope is because otherwise the RTM API wouldn't work.
+ We might remove the RTM API usage in newer version of this bot. Make sure to
+ install the app to the workspace. When successful, you should see a token
+ that starts with "xoxb-...". There is also a token that starts with
+ "xoxp-...", we need the "xoxb-..." one.
+3. Go to "App Home", click the button "Add Legacy Bot User".
+4. (Important) Make sure the bot is subscribed to the channel. You can do this by typing e.g. `/invite @zulip_mirror` in the relevant channel.
+5. In the `slack` section of the Zulip-Slack bridge configuration file, enter the bot name (e.g. "zulip_mirror") and token, and the channel ID (note: must be ID, not name).
### Running the bridge
