Docs: define better terminology for feature flags

Discussion from !40518 (comment 403944373):

Marcia says:

@m_gill I've noticed that the two things are confusing for our team members: the "Feature Flags" feature we offer as part of the product versus the feature flags we use to develop GitLab. If it's confusing for our team, I guess it's confusing for our users too.

Any ideas how could we make this clearer for everyone? Maybe we could rename our FF process to something else, like, "Feature rollout" or just something else rather than "feature flags"? I'm not sure, just brainstorming to see if we can get different terms. 🤔

Michelle says:

@marcia there has been talk about this before in Slack - my recommendation is that it should be a whole new issue, since there isn't a clear solution to the problem. You will also find me personally using the terms "Unleash" and "Flipper" for this reason (to distinguish the difference in what I'm talking about) - which I don't think this is a good behavior, because we should be referring to our in-product feature flags by the nomenclature instead of "Unleash."

Proposal

Either:

  1. Keep it as a feature term:
  • a) GL product: Keep the term "Feature Flags" to preserve the original product terminology on behalf of the users.
  • b) GL dev: Rename to "Feature flippers"? Sounds good, but it wouldn't read as good as it sounds, I think. For example, "This feature was deployed behind a feature flipper. To enabled it, do X."
  1. Keep it as a dev term:
  • a) GL product: Rename it to "Feature Toggles", which is a term well known by the dev community.
  • b) GL dev: keep it as "Feature Flag".

@m_gill @cnorris @sselhorn WDYT?