* fix(actions): use a specific shortening length for SHAs
The rlespinasse/github-slug-action now works without checking out the code, reduce time and improving security with following actions.
This requires to specify the GITHUB_SHA_SHORT variable length, as git uses 8 by default, but docker uses 7 by default.
* fix(actions): target correct rlespinasse/github-slug-action version
* fix(actions): just use major version
* fix(actions): github-slug-action is not being correctly referenced