## 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
