[$100] Make the app which uses client slack lambda distributable

[billsedison]

Configure client Slack lambda app to have redirect URL configured so that our app which uses client slack lambda is distributable, and we don't want to make TC slack lambda distributable.

Submission Guideline

• Update the code
• Update the Deployment guide and verification doc accordingly

[MayurRJoshi]

@billsedison Should I work on the updated code from the ms teams integration challenge instead of the code in the repo?

[MayurRJoshi]

My PR would then include changes made for that challenge

[billsedison]

Should I work on the updated code from the ms teams integration challenge instead of the code in the repo?
@MayurRJoshi Yes, please, thanks.