Job name for a branch with a slash is double escaped in job URL:
https://jenkins.mydomain.com/view/myview/job/github_org/job/github_repo/job/first_part_of_branch%252Fpart_of_branch_after_slash/
Note that slash in branch first_part_of_branch/part_of_branch_after_slash was escaped twice, giving %252F.
A path to artefacts also contains double escaped slash.

Pipeline command echo env.JOB_NAME prints job name with branch name escaped once:
github_org/github_repo/first_part_of_branch%2Fpart_of_branch_after_slash/
Slash escaped once to %2F.

As a result of this inconsistency, env.JOB_NAME cannot be used to communicate job and artefacts URLs to 3rd party services.