Improve Netlify deployment message

[tbouffard]

Currently, when the deployment is triggered by a doc-site change, we only display the commit sha from the bonita-documentation-site repository.

We could add a prefix like 'site update' and use a short commit sha (as also suggested for #228) and always remove the Deploy prefix which is implicit (this includes deployment triggered by documentation content change).
For instance site update 1d69bc0

We should do the same when triggered manually

• current: Deploy ${{github.sha}} from manual request
• proposal: site request 1d69bc0

Proposal Summary

The message form will be <source> <type> <short_sha>
For instance

• bonita-2021.2 update 1d69bc0. Notice that documentation source repository can trigger production deploy with a workflow_dispatch as well. If we want the information, it should be passed in the repository_dispatch event as we want to do for Netlify: track the commit of the documentation content repository that triggers the deploy #228
• site update 1d69bc0
• site request 1d69bc0 or site manual-request 1d69bc0

Resources for short sha

• https://github.com/marketplace/actions/short-sha
• https://github.com/allenevans/short-sha
• directly with bash: https://github.community/t/add-short-sha-to-github-context/16418/3
• ... to be continued

About the message construction

Currently, the message is built by using several steps that are run depending of the availability of some values in the input event and they are written in bash.
The maintenance is not easy and this will be harder with the requirements described in this issue.
We could switch the implementation to JavaScript that allows easy string transforms.
This could be done by using https://github.com/actions/github-script or setting the step shell to shell: node {0}

steps:
  - name: Use JavaScript to defined the step content
    shell: node {0}
    run: |
      // my super JavaScript code here