Slack Slash commands use the channel ID, not the name
In https://gitlab.com/gitlab-org/gitlab-ee/blob/1ef9b3ebaa50ca09e3bff8548501edd33abf7696/ee/lib/gitlab/slash_commands/run.rb#L29, we send the Slack channel ID rather than the name.
This is good because the ID is static and won't change even if the channel is renamed. It's bad because not being able to use the name of the channel isn't very user-friendly.
This value ends up being passed to the CI job as a CHAT_CHANNEL
environment variable.
I think we should start providing the name. For backwards compatibility it probably needs to be in addition to the ID. Maybe by adding a CHAT_CHANNEL_NAME
variable?