[NEXUS-7814] Ban UID from containing relative paths
[NEXUS-7814] Re-implement repository file resolution, simplify and use canonical files to verify parent/child relationship
[NEXUS-7814] Refine exception text
[NEXUS-7815] replace use of getCanonicalFile() with java.nio.file toPath().toAbsolutePath().normalize()
[NEXUS-7815] test handling of relative paths