Issue #38 — Backend: PDF Invoice Generation Provider

[yusuftomilola]

Location: backend/src/invoices/providers/pdf-invoice.provider.ts

Description

Every invoice on ManageHub should be available as a downloadable PDF. This provider accepts an invoice (with its relations loaded) and returns a Buffer containing a formatted PDF document. The buffer is used in two places: as an email attachment (Issue #40) and as the response body for the download endpoint (Issue #39).

Use the pdfkit npm package (npm install pdfkit + npm install --save-dev @types/pdfkit) to generate the PDF programmatically. The document does not need to be elaborate — clean, readable, and professional is sufficient.

Acceptance Criteria

• A PdfInvoiceProvider class is created at backend/src/invoices/providers/pdf-invoice.provider.ts
• The provider exposes a generate(invoice: Invoice): Promise<Buffer> method where invoice has user, booking, and booking.workspace relations loaded
• The generated PDF includes the following sections:
  • Header — ManageHub logo/name, "TAX INVOICE" title
  • Invoice metadata — Invoice number, issue date, payment date
  • Bill To — Member's full name and email address
  • Service details — Workspace name, plan type, start date, end date, number of seats
  • Amount summary — Subtotal, total amount in Naira (₦), status (PAID)
  • Footer — "Thank you for your business" or equivalent
• The method returns a Buffer (not a stream) so it can be attached to emails and sent as an HTTP response
• PdfInvoiceProvider is registered in InvoicesModule providers and exported
• pdfkit is added to backend/package.json dependencies
• npx tsc --noEmit passes with no errors