Make names case-insensitive

Names, especially executor names, should be case-insensitive. Currently its possible to create two executors (or services, environments, etc) with names that differ only in case of letters. This behaviour can lead to hard-to-debug errors and should be changed.

Start by locating the creation and name-handling paths for executors, services, environments, and other named resources. Check how names differing only by letter case are currently accepted, then verify that such duplicates are consistently rejected across each resource type.

Written by the indexing model from the issue text.