Slack Bot

In last few commits, I have implemented a basic Slack bot functionality. This is how it works:

• Users can add the bot to their workspace by going to https://learnawesome.org/join_slack

• This slack app needs the following Oauth permission scopes: chat:write, chat:write.public, commands

• Once the permission is granted, the access token is stored in SlackAuthorization table.

• This bot currently adds two slash commands: /startlearning [topic] and /stoplearning [topic]. Using these commands, slack teams' channels can subscribe/unsubscribe to topics. These subscriptions are kept in SlackSubscription table which has a schema (slack_authorization_id, channel_id, topic_id)

• Whenever a new item is created, all such channels are notified by SlackSubscriptionNotifyJob.

• This is different from SlackNotifyJob which is used only in our own slack to post items from ALL topics to the #new-items channel. BTW, we also post a random topic to our #general channel in SocialMediaUpdatesJob every day at 13:00 UTC.

Enhancement ideas

• Post daily updates to slack subscriptions so that they don't have to wait till a new item gets added
• Enable conversations and on-demand resources