GHSA-2FC9-XPP8-2G9H `@backstage/backend-common` vulnerable to path traversal through symlinks

Impact Paths checks with the resolveSafeChildPath utility were not exhaustive enough, leading to risk of path traversal vulnerabilities if symlinks can be injected by attackers. Patches Patched in @backstage/backend-common version 0.21.1. Patched in @backstage/backend-common version 0.20.2. Patch...