[ spike ] Discover and Promote the best way to install Upsun CLI in GitHub actions

[apotek]

Description

Research best way to install Platform/ Upsun CLI into our GitHub actions.

Implement that: Document and evangelize the approach

Investigating a better way to install the Upsun CLI (using their action)?

This came from Engineering Council agenda.

[apotek]

Looks like Upsun is maintaining a GitHub action for installing the Upsun / Platform CLI

https://github.com/upsun/action-cli

[apotek]

Related: https://github.com/ChromaticHQ/benz-tickets/issues/5059