set proglang based on exenv

try to guess exenv based on proglang

app/services/proforma_service/convert_exercise_to_task.rb

@@ -23,7 +23,7 @@ module ProformaService
           title: @exercise.title,
           description: @exercise.description,
           internal_description: nil,
-          # proglang: proglang, where can we get this information?
+          proglang: proglang,
           files: task_files,
           tests: tests,
           uuid: uuid,
@@ -44,6 +44,12 @@ module ProformaService
       )
     end
 
+    def proglang
+      regex = %r{^openhpi/co_execenv_(?<language>[^:]*):(?<version>[^-]*)(?>-.*)?$}
+      match = regex.match @exercise.execution_environment.docker_image
+      match ? {name: match[:language], version: match[:version]} : nil
+    end
+
     def uuid
       @exercise.update(uuid: SecureRandom.uuid) if @exercise.uuid.nil?
       @exercise.uuid