Support custom request ID

[renatomassaro]

Closes #323

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If the client sends a request_id alongside the request parameters, the response will include this same request_id, and any events fired as a result/side-effect of this request will also contain the request_id.

Incidental

• Simplified ProcessCreatedEvent.Notificable implementation by delegating the full/partial access logic to the correct place (ie the renderer at PublicProcessView, which delegates to Process.Viewable).
• Minor improvements on the interface of Public and Flow methods
• Moved the Logout request from the Requests channel to the Account channel.
• Removed the now useless Requests channel.
• Removed previously used X-Request-Id HTTP header

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This change is 

[sourcelevel-bot[bot]]

Ebert has finished reviewing this Pull Request and has found:

• 1 fixed issue! 🎉

You can see more details about this review at https://ebertapp.io/github/HackerExperience/Helix/pulls/329.

[renatomassaro]

Reviewed 58 of 58 files at r1. Review status: all files reviewed at latest revision, 2 unresolved discussions.

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lib/software/public/index.ex, line 56 at r1 (raw file):

  end

  def render_file(file = %File{}) do

spec

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lib/websocket/request.ex, line 121 at r1 (raw file):

end

defmodule Helix.Websocket.Request.Relay do

move to a separate file

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Comments from Reviewable

[renatomassaro]

Reviewed 11 of 11 files at r2. Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable