Event payload of the `message` event does not have a consistent schema (missing `team` property when message subtype is `file_share`)

[sorsaffari]

Description

event payload of the message event is missing the team property when the message contains files (i.e. subtype is file_share).

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

• [x] bug
• [ ] enhancement (feature request)
• [ ] question
• [ ] documentation related
• [ ] testing related
• [ ] discussion

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

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

---

Bug Report

Reproducible in:

Development environment: Mac OS 11.2, Node.js 14.15.4, Bolt.js 3.4.0

Steps to reproduce:

1. perform the required configurations of a Slack app to listen to the message event
2. post a message with text only (no files attached)
3. observe the event payload
4. post a message with a file attached
5. observe the event payload

Expected result:

The event payload in steps 3 and 5 both include the team property

Actual result:

The event payload in step 3 includes the team property and the one in step 5 doesn't