Migrate `master` branch to `main`

[Zeitsperre]

This is something we have been progressively doing across all the Ouranosinc code repositories. I don't imagine it would be too controversial/breaking to perform that here as well.

@tlvu how much of a disruption would such a change be here?

[tlvu]

You'll have to ensure notebook autodeployment still works, this line to change https://github.com/Ouranosinc/PAVICS-e2e-workflow-tests/blob/81987bf3fbcdfc057f63a11af15738e1ba587e7b/default_build_params#L32

And Jenkins will test the new branch name: https://github.com/Ouranosinc/PAVICS-e2e-workflow-tests/blob/81987bf3fbcdfc057f63a11af15738e1ba587e7b/Jenkinsfile#L62

Same process if you want to change pavics-sdi, PAVICS-landing, Raven, RavenPy repos. Together with Finch, those are the 5 repos we autodeploy notebooks to PAVICS and we run Jenkins nightly test on them.

The tricky part is the rename in the 5 repos and the merge in the PAVICS-e2e-workflow-tests repo have to be done in sync, at the same time.

That said, if we have users that bookmarked the various tutorials notebooks and their old links contain master, they will break. But leaving the old master name behind, they will get old stale version without knowing about it. Same problem if our users have existing clone/checkout of the 5 repos.

So I wonder if we have a mean to notify our users to soften the blow of this change.