This is motivated by a race condition when loading archived messages (calling Candy.View.Pane.Message.show) at the same time as rendering an incoming message, such as when a 1-on-1 message arrives and auto-opens a new pane for the chat partner.
Coverage remained the same at 56.62% when pulling 9c0fec985c27a0be1887e59715907614622d79f5 on feature/avoid-duplicate-message-ids into 9cd70225157d0e54ab0c51a77c7e00aea7414ee2 on dev.
This is motivated by a race condition when loading archived messages (calling Candy.View.Pane.Message.show) at the same time as rendering an incoming message, such as when a 1-on-1 message arrives and auto-opens a new pane for the chat partner.