Expose a "created by" attribute in feature flags

Problem to solve

It would be good to expose information about the user who created a feature flag through the feature flags API.

Intended users

Further details

Being able to fetch which user created or modified a feature flag through the API is important to a number of internal tooling use cases. This information is available in the projects audit log, but IMO should be included in the JSON response.

One use case would be to include this data in internal auditing tools, or use it to remind the user about a feature flag after a certain number of weeks of it being enabled.

Proposal

Modify the JSON response for the single (or list) flags API to include:

{
    "created_by": "tom@home.net",
    "modified_by": "james@home.net"
}

Links / references

Edited by Tom Forbes