Add a new .../:feature/variants API
This adds
- `GET /api/admin/projects/:projectId/features/:featureName/variants` which returns
```json
{ version: '1', variants: IVariant[] }
```
- `PATCH /api/admin/projects/:projectId/features/:featureName/variants` which accepts a json patch set and updates the feature's variants field and then returns
```json
{ version: '1', variants: IVariant[] }
```
- `PUT /api/admin/projects/:projectId/features/:featureName/variants`
which accepts a IVariant[] and overwrites the current variants list for the feature defined in :featureName and returns
```json
{ version: '1', variants: IVariant[] }
- This also makes sure the total weight of all variants is == 1000
- Validates that there is at least 1 'variable' variant if there are variants
- Validates that 'fix' variants total weight can't exceed 1000
- Adds tests for all these invariants.
Co-authored-by: Simon Hornby <simon@getunleash.ai>
Adds environment support
This PR adds environments as a first-class concept in Unleash.
It necessitated a full rewrite on how we connect feature <-> strategy, as well as a rethink on which levels environments makes sense.
This enables PUTs on strategy configurations for a feature, since all strategies now have ids.
This also updates export/import format. The importer handles both formats, but export is no longer possible in version 1 of the export format, only in version 2, with strategy configurations for a feature as a separate object.
Co-authored-by: Christopher Kolstad <chriswk@getunleash.ai>
Co-authored-by: Fredrik Oseberg <fredrik.no@gmail.com>
Co-authored-by: Ivar Conradi Østhus <ivarconr@gmail.com>
