Change billing statements to generate line items in the new format for inbound and outbound messages
Add billing migration after LineItems model changes
Update billing admin read only fields to match LineItem model field changes
Update billing test helpers to pass the correct args to generate_account_statement() after changing the args it expects
Update billing statement rendering to match the model changes
Allow LineItem model's channel and channel type fields to be null
Fix billing admin tests
Fix billing invoice template to render tagpool display name correctly
Sort line items by their description when rendering statements to a pdf
Ensure line items are in the right order before doing a groupby when rendering statements to pdf
Remove forgotten debugging lines
Actually ensure line items are in the right order before doing a groupby when rendering statements to pdf
Use billing test helpers in task tests
Change billing statement task args back to how they were to keep celery happy
Merge branch 'develop' into feature/issue-1060-update-statement-generation
Merge branch 'feature/issue-1060-update-statement-generation' into develop