Add helper function parse_subscription_export_csv() which parses the csv format returned by the subscription exporter

src/invidious/helpers/utils.cr

@@ -1,3 +1,5 @@
+require "csv"
+
 # See http://www.evanmiller.org/how-not-to-sort-by-average-rating.html
 def ci_lower_bound(pos, n)
   if n == 0
@@ -367,3 +369,23 @@ def fetch_random_instance
 
   return filtered_instance_list.sample(1)[0]
 end
+
+def parse_subscription_export_csv(csv_content : String)
+  rows = CSV.new(csv_content, headers: true)
+  subscriptions = Array(String).new
+
+  rows.each do |row|
+    # Channel ID is the first column in the csv export we can't use the header
+    # name, because I believe the header name is localized depending on the
+    # language the user has set on their account
+    channel_id = row[0].strip
+
+    if channel_id.empty?
+      next
+    end
+
+    subscriptions << channel_id
+  end
+
+  subscriptions
+end