Write ADR for feature flags

[ccostino]

In order to make it easier to deploy changes to production, A/B test features and UI/UX improvements, and turn things on/off if need be, our application needs to be able to incorporate the use of feature flags.

There are several ways to go about this, and the feature flags need to be able to work across the following dimensions:

• API app code
• Admin app code
• Admin front-end code
• Handled independently across environments

Therefore, we'd like to write up an ADR that considers the merits of a few different approaches and generate discussion within the team for the best path forward.

Implementation Sketch and Acceptance Criteria

• Research a few ways on how feature flags can be implemented (with an eye toward Python and JavaScript) that address the constraints listed above
• Create a new ADR ties together the research and one or two proposed approaches
• Discuss the ADR with the team and settle on an approach
• Write an issue to follow up with implementation of feature flags and update the ADR

Security Considerations

• Account for making sure no sensitive information or credentials are exposed in doing this work.
• Think through the implications of feature flags on things that have security compliance requirements with them.