Executive Summary: Currently, the Subscription Billing module lacks the flexibility to "pause" billing without terminating lines. This proposal enables setting a quantity of 0 in subscriptions and usage data imports to allow billing gaps without breaking the "Next Billing Date" continuity.

Current Problem: * Importing usage data with quantity 0 causes errors.

• There is no native way to skip a billing period while keeping the contract active, leading to manual workarounds and potential billing gaps.

Proposed Solution:

• Allow Quantity 0: Enable the Quantity field to accept 0. Add a confirmation dialog: "If you set the quantity to 0, the billing will pause until further notice but the subscription lines are not terminated. Do you want to continue?"
• Usage Data Support: Update the "Process Imported Lines" and "Create Usage Data Billing" functions to accept and process lines with quantity 0 instead of throwing an error.
• Logic Continuity: When a period is "billed" with quantity 0, the system should still increment the Next Billing Date to the following period to ensure no gaps occur when usage resumes.
• Document Creation: Billing and posting lines should be created with quantity 0. Printing will follow existing system settings for zero-quantity lines.

Business Value: Allows companies to support "seasonal" or "on-hold" customers without administrative overhead or data loss. Ensures usage-based billing accurately reflects periods of zero consumption in the customer's history.