[Summer OSPP 2024] Karmada supports smooth rollback of a single cluster

[chaosi-zju]

What would you like to be added:

Karmada supports joining a single cluster and promoting the existing resources from the original cluster. It also supports unjoining a single cluster and removing it from Karmada's control. When unjoining a single cluster, Karmada cleans up resources on the cluster that were previously controlled by Karmada, but in some removal scenarios, users want these resources to continue to remain in the single cluster.

Karmada hopes to attract more users to try to evolve from a single cluster to a multi-clusters. This ability can reduce the trial-and-error costs of users. When users want to fall back from multi-clusters to a single cluster, it can minimize the impact on the single cluster after rollback.

Therefore, we plan to provide a smooth rollback capability. When removing a managed cluster, users can choose to retain the resources in the original cluster.

Project link: https://summer-ospp.ac.cn/org/prodetail/245c40436

Parts of: #4879

Desired outcomes:

• guarantee the promotion can be rolled back safely guarantee the promotion can be rolled back safely #5601
• support unregister a pull mode cluster in karmada support unregister cluster in karmada #5626
• add realted e2e for migration rollback feature add e2e for migration rollback feature #5609
• add realted ut for migration rollback feature [WIP] add realted ut for migration rollback feature #5628
• add tutorial doc in website repo about how to do migration rollback [WIP] add tutorial doc in website repo about how to do migration rollback website#698
• add administrator doc in website repo about how to do migration rollback [WIP] add administrator doc in website repo about how to do migration rollback website#697
• support preserving resource in member cluster when executing karmadactl unjoin #5594

[wulemao]

/assign