[BUG]: 0 Units volume pricing flat fee is not applied without usages

[grthr]

Describe the bug
The flat fee of a volume pricing metered charge should be charged without any usages being send. According to the UI it applies starting from first unit = 0.

So I would expect the minimum charge without any usage metrics would be Subscription Fee + Flat fee of Volume pricing's first row. Instead, only the Subscription fee is billed.

To Reproduce
Steps to reproduce the behavior:

1. Add a plan with a metered charge and charge mdel Volume pricing
2. Set a flat fee of 50 $ in first row (keep default from 0 to 1 units)
3. Set the same or a higher flat fee in the second row.
4. Wait for the invoice to be created without sending usages.
5. The invoice does not contain the flat fee of the first row of the volume pricing.

Support

• Version v1.26.1