Description:

Currently, all messages are public to all users who can view the channel. When implementing a bot, this bot has to be able to interact with a particular user inside the channel: It needs to e. g. ask him to provide further information or guide him through a process. All this interaction (which happens only between the bot and one user) needs to be hidden from other user's eyes in order to make the channel readable.
This is particularly important with respect to the Rocket.Chat apps (#6890) which might also want to provide interaction with one user.

Server Setup Information:

• Version of Rocket.Chat Server: 0.59

Expected behavior:

As a user, I want to be able to interact with a bot without the rest of the channel noticing it.

Actual behavior:

All messages are visible to everybody

Proposal:

• Implement a particular message property that makes the message visible for particular users only and render it differently.
• Ideally, the user could also confirm the message so that it appears less disruptive in his timeline
• Provide an API to be consumed from the Rocketlets (see https://api.slack.com/methods/chat.postEphemeral)