Add a way to turn off web page rendering for "/slack/install"

[seratch]

Description

As described at #732 , there is no way to directly redirect installers to the authorize url with the out-of-the-box receivers. Also, the code that generates the /slack/install endpoint is not yet customizable for developers.

Workaround

a workaround as of today is to implement your own /slack/install endpoint using receiver.router. Refer to this document to know how to add your custom endpoints to Bolt apps.

You can use the custom endpoint for Direct install URL of an App Directory app. To learn how to generate a valid set of parameters, checking this code is helpful. Your app can set a generated URL for "Location" header along with status 302 in response to HTTP requests.

const url = await this.installer!.generateInstallUrl({
  metadata: installerOptions.metadata,
  scopes: scopes!,
  userScopes: installerOptions.userScopes,
});

Solution

In Bolt for Python (and also Bolt for Java), we have an option to switch to a Direct Install URL compatible behavior. slackapi/bolt-python#183

We can add a similar option to change the behavior. If the page rendering is disabled (default: enabled), Bolt redirects installers to generated authorize URL.

What type of issue is this? (place an x in one of the [ ])

• bug
• enhancement (feature request)
• question
• documentation related
• example code related
• testing related
• discussion

Requirements (place an x in each of the [ ])

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.