This PR changes the payload of the strategiesBySegment endpoint when the
flag is active. In addition to returning just the strategies, the object
will also contain a new property, called `changeRequestStrategies`
containing the strategies that are used in change requests.
This PR does not update the schema. That can be done later when the
changes go into beta. This also allows us some time to iterate on the
payload without changing the public API.
## Discussion points:
Should `strategies` and `changeRequestStrategies` ever contain
duplicates? Take this scenario:
- Strategy S uses segment T.
- There is an open change request that updates the list of segments for
S to T and a new segment U.
- In this case, strategy S would show up both in `strategies` _and_ in
`changeRequestStrategies`.
We have two options:
1. Filter the list of change request strategies, so that they don't
contain any duplicates (this is currently how it's implemented)
2. Ignore the duplicates and just send both lists as is.
We're doing option 2 for now.
This PR hooks up the changes introduced in #5301 to the API and puts
them behind a feature flag. A new test has been added and the test setup
has been slightly tweaked to allow this test.
When the flag is enabled, the API will now not let you delete a segment
that's used in any active CRs.
## About the changes
- Refactored some E2E tests to use our APIs
- Added test cases for project-specific segments
- Added validation to check a project can access a specific segment
- Fixed an OpenAPI schema that was missing segments
## Discussion points
https://github.com/Unleash/unleash/pull/3339/files#r1140008992
## About the changes
- Introducing ISegmentService interface to decouple from the actual
implementation
- Moving UpsertSegmentSchema to OSS to be able to use types
- Added comments where our code is coupled with segments just to
highlight and have a conversation about some use cases if needed, but
they can be removed before merging
- Removed segment service from some project features as it was not used
