[Bug][Extensibility][SubscriptionBilling]: Missing extensibility for Usage Data Billing in Sales Invoice printout

[AndreasAtRocket365]

Describe the issue

We are implementing a scenario where imported usage data needs to be displayed in the attachment of posted sales invoices.

Currently, this is not properly extensible:

• It is very complex to propagate fields from Usage Data Generic Import to Usage Data Billing
• It is not possible to extend the dataset of report "Standard Sales - Invoice" to include additional fields from Usage Data Billing (missing integration events / entry points)

Additionally, we need to control when the attachment is created:

• Only invoice lines with usage data should generate attachment entries
• No attachment should be created for subscription lines without usage data

Expected behavior

• Simple and standard way to pass additional fields from Usage Data Generic Import to Usage Data Billing
• Integration events before inserting Usage Data Billing and Billing Line Archive into the temp buffer used for printout
• Ability to enrich the dataset of the Sales Invoice report via standard extensibility
• Control over which lines appear in the attachment

Steps to reproduce

1. Import usage data via Usage Data Import / Generic Connector
2. Ensure data is processed into Usage Data Billing
3. Post a Sales Invoice for a subscription contract with usage-based billing
4. Open/print report "Standard Sales - Invoice" (with Contract Billing details)
5. Try to:

• Extend the dataset with additional fields from Usage Data Billing (e.g. imported product name)
• Control which lines appear in the attachment

Additional context

A full implementation (codeunit and reportextension changes) is provided in the related pull request.

I will provide a fix for a bug

• I will provide a fix for a bug