2.8.0rc5: Bug fixes and document updates

What's Changed

• [2.8] Clarify Externalizer nested list subclass caveat by @nvidianz in #4719
• [2.8] Fix dashboard container launch from installed package by @chesterxgchen in #4720
• [2.8]: Avoid name collision in Dockerfile by @IsaacYangSLA in #4727
• [2.8] Fix external process max_resends serialization by @chesterxgchen in #4724
• [2.8] Prevent corrupt client API models from incomplete downloads by @chesterxgchen in #4725

Full Changelog: 2.8.0rc4...2.8.0rc5