Enable Deactivated User Search by Email

[mw-root]

Description

This PR implements the bug described in #251.

GetUserByEmailContext is very fast but does not find deactivated users.

I've added a new func called searchByEmail that mirrors searchByName.

It is not used by default because it is quite slow when polling many users. Instead it is only called if GetUserByEmailContext fails with users_not_found and include_deactivated is true.

Example

Default Functionality

data "slack_user" "test" {
  email = "deactivated.user@domain.com"
}

╷
│ Error: not found deactivated.user@domain.com: users_not_found
│
│   with data.slack_user.test,
│   on main.tf line 1, in data "slack_user" "test":
│    1: data "slack_user" "test" {
│

Include Deactivated

data "slack_user" "test" {
  email               = "deactivated.user@domain.com"
  include_deactivated = true
}
output "slack_user" {
  value = data.slack_user.test
}

Changes to Outputs:
  + slack_user = {
      + email               = "deactivated.user@domain.com"
      + id                  = "UXXXXXXXX"
      + include_deactivated = true
      + name                = "deactivated.user"
    }