Fix issue where pvc range produced multiple volume keys

[paimonsoror]

Resolves #135

Confirmed the following via tests:

• Inclusion of storage.existingVolumeClaim does not create a volume key in the deployment
• Omitting storage.existingVolumeClaim and creating either/or/both of storage.data / storage.attachments creates a single volume key with children for each

(dont judge my test keys lol as i had to spoof the volumeClaim names to avoid errors with includes in my test)

[santiagon610]

LGTM 🚀

[paimonsoror]

@guerzon how are you feeling about this one

[guerzon]

Thanks @paimonsoror for the PR.