[ch89835] Migrate DO subscription information in inter-cloud migrations

[Shylpx]

Resources

• Clubhouse story

Context

• When a user is migrated from one cloud to another, we need to migrate the information about DO subscriptions stored in Redis.

Changes

• Export/import information stored in Redis about DO subscriptions.
• Add tests

[shortcut-integration]

This pull request has been linked to Clubhouse Story #89835: Inter-cloud migrations may leave redis keys behind.

[rafatower]

First time I see that RedisExportService o_O

I do agree with ignoring those RSpec/InstanceVariable rubocop complaints

There's a timeout in the onprem build, and seem to happen in the licensing service. I'd ask Infra to sort that out.

Other than that, looks fine to me 👍