Feature Request: prefix string for result backend

[Graeme22]

Hi, thanks for this great project!

When using Redis to store results, it might be nice to be able to add a prefix to the key to better organize the database. RedisInsight, for example, organizes keys into folders based on the : separator.

If desired I can submit a PR.

[s3rius]

That would be nice to have. PRs are always welcome.