We introduced `pages_update_legacy_storage` feature flag(enabled by default). When disabled this feature flag will stop updating pages on disk storage(NFS), so we stop: * updating pages when new deployments happens * update pages configuration * move pages when projects/groups got moved * remove pages when users press "remove pages", or when project/group are removed This feature flag is not scoped to the project because it can lead to an inconsistent state on disk when projects are moved. Currently, we can't disable the feature flag until: 1. [we migrate all the data on .com](https://gitlab.com/groups/gitlab-org/-/epics/3909) 1. [we stop serving from legacy storage](https://gitlab.com/gitlab-org/gitlab/-/issues/297524) But we still can prepare all the relevant code. The next plan is very similar to https://gitlab.com/groups/gitlab-org/-/epics/3980: 1. every time rails code accesses pages_path we report an error to sentry 1. fix all of these reported cases 1. raise an actual error if serving from legacy storage is disabled 1. ask infrastructure team to verify that there is no write operations on the pages NFS share, and give them a green light to disconnect it