Moodle uses the course shortname as an identifier for external tools. This is not configurable, so if your cours shortname format violates your external tool provider's requirements for 'course identifier', you will be unable to use that external tool without refactoring your course shortname-ing scheme.
Discovered while working with the Echo360 LTI:
1. Echo360 LTI does not allow spaces in the external (Moodle) course identifier
2. Moodle LTI mod uses course->shortname as the course identifier AND Moodle allows spaces in course shortname
3. We use spaces in our course shortnames
I will attach a patch that makes this setting configurable