PVC and containers shared the same ResourceRequirements struct to define their
API. When resource claims were added, that struct got extended, which
accidentally also changed the PVC API. To avoid such a mistake from happening
again, PVC now uses its own VolumeResourceRequirements struct.
The `Claims` field gets removed because risk of breaking someone is low:
theoretically, YAML files which have a claims field for volumes now
get rejected when validating against the OpenAPI. Such files
have never made sense and should be fixed.
Code that uses the struct definitions needs to be updated.
PVC and containers share the same ResourceRequirements struct. The Claims field
in it only makes sense when used in containers. When used in a PVC, the field
should have been rejected by validation. This was overlooked when introducing
it, so now persisted objects might have it set and/or people may have started
to rely on it being accepted even when it has no effect.
Therefore we cannot reject it in validation anymore, but we can still strip
it out on create or update.
Modify the behavior of the AnyVolumeDataSource alpha feature gate to enable
a new field, DataSourceRef, rather than modifying the behavior of the
existing DataSource field. This allows addition Volume Populators in a way
that doesn't risk breaking backwards compatibility, although it will
result in eventually deprecating the DataSource field.
Update the unit tests to include checks for incorrect APIGroup type in
PVC DataSource and change the name of the feature gate to be more clear:
s/VolumeDataSource/VolumePVCDataSource/
