Generate invocies from the members.csv

This commit updates the previous template to inline the two images as
data URIs and embed ERB template markers for the data. The ruby script
added in this commit interpolates the data from the members.csv file
into the template and generates PDFs using wkhtmltopdf.

scripts/generate_invoices.rb

@@ -0,0 +1,66 @@
+require 'csv'
+require 'erb'
+require 'date'
+
+FIRST_INVOICE_NUMBER = 50
+
+output_dir = File.join(File.dirname(__FILE__), "..", "invoices", "sent", "2022")
+
+members_fn = File.read(File.join(File.dirname(__FILE__), "..", "members.csv"))
+members = CSV.parse(members_fn, headers: true)
+
+template_fn = File.read(File.join(File.dirname(__FILE__), "..", "template", "template.html"))
+
+class Invoice
+  def initialize(data, number)
+    @coop_name = data['coop_name']
+    @contact_address = data['contact_address']
+    @members = data['members']
+    @number = number
+  end
+
+  def date
+    Date.today.strftime('%d %B %Y')
+  end
+
+  def number
+    "%04d" % @number
+  end
+
+  def members
+    @members.to_i
+  end
+
+  def total
+    members * 52
+  end
+
+  def name
+    @coop_name
+  end
+
+  def basename
+    name.downcase.gsub(' ', '_').gsub('.', '')
+  end
+
+  def address
+    @contact_address.gsub("//", "\n")
+  end
+
+  def get_binding
+    binding()
+  end
+end
+
+members.each_with_index do |member, index|
+  invoice = Invoice.new(member, FIRST_INVOICE_NUMBER + index)
+  renderer = ERB.new(template_fn)
+  result = renderer.result(invoice.get_binding)
+
+  output_html_fn = File.join(output_dir, invoice.basename + '.html')
+  output_pdf_fn = File.join(output_dir, invoice.basename + '.pdf')
+
+  File.write(output_html_fn, result)
+
+  system("wkhtmltopdf #{output_html_fn} #{output_pdf_fn}")
+end