Users cannot sign up while being a Slack User

[marcelogdeandrade]

Overview

If a user starts using Onyx through a Slack Bot, he is automatically signed up as a Slack User. However if I want to change the role of that user to a different one, such as Basic or Admin, I need to invite them so they can create their password during sign up.

The issue here is that during sign up I'm getting the following error:

Failed to login - Create an account to set a password.

Steps to reproduce:

1. Deploy Onyx 0.20.0 with a Slack Bot
2. Send a message to the slack bot to create a Slack User account with your slack email
3. As an admin, go to the web ui and invite the account that is currently a Slack User
4. Try to sign up to Onyx using the invited email