Is your feature request related to a problem? Please describe.
I would love the ability to force myself into a specific variant of a flag on a per-request basis in order to facilitate the testing of flags that are currently either disabled or set to 0%.

Describe the solution you'd like
As a developer, I need the ability to force myself into a specific variant or combination of variants across flags in order to test things in a production environment before we've begun targeting live production traffic with those flags. Ideally, I would be able to specify the overrides via a query param or HTTP header and then pass those overrides to the LD Client during bucketing.

There may be security concerns associated with users being allowed to force bucket themselves into different variants, but the responsibility of addressing those concerns should fall on me as the application developer and not the LD client. For example, I should check the client IP and only respect the requested overrides if the request is from an IP address on my internal network.

Describe alternatives you've considered
Today, I can achieve the above via custom targeting rules on a flag. However, this becomes cumbersome when trying to implement this opt-in behavior in a consistent manner across all flags.

Additional context
Other feature flag providers provide this functionality:

• Optimizely: https://docs.developers.optimizely.com/full-stack/docs/use-forced-bucketing
• Rollout.io (in a limited capacity only for browser and native clients): https://docs.cloudbees.com/docs/cloudbees-feature-flags/latest/debugging/override-view