Improve markdown support and tweak sponsorship langage

app/helpers/format_helper.rb

@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+require 'redcarpet/render_strip'
 
 module FormatHelper
   ##
@@ -206,6 +207,11 @@ module FormatHelper
     markdown("#{text} Please look at #{link_to '**Markdown Syntax**', 'https://daringfireball.net/projects/markdown/syntax', target: '_blank'} to format your text", false)
   end
 
+  # Return a plain text markdown stripped of formatting.
+  def plain_text(content)
+    Redcarpet::Markdown.new(Redcarpet::Render::StripDown).render(content)
+  end
+
   def quantity_left_of(resource)
     return '-/-' if resource.quantity.blank?
 

app/views/conferences/_sponsors.haml

@@ -27,9 +27,9 @@
       .row
         .col-md-12
           %h3.text-center
-            Want to sponsor?
+            = "Interested in sponsoring #{conference.title}?"
             = link_to(sponsorship_mailto(conference)) do
-              Contact us!
+              Please, contact us!
 
 - sponsors.each do |sponsor|
   - content_for :modals do

app/views/conferences/show.html.haml

@@ -1,10 +1,10 @@
 - content_for :head do
   %meta{ property: "og:title", content: @conference.title }
   %meta{ property: "og:site_name", content: (ENV['OSEM_NAME'] || 'OSEM') }
-  %meta{ property: "og:description", content: @conference.description }
+  %meta{ property: "og:description", content: plain_text(@conference.description) }
   %meta{ property: "og:url", content: conference_url(@conference.short_title) }
   %meta{ property: "twitter:title", content: (@conference.title) }
-  %meta{ property: "twitter:description", content: @conference.description }
+  %meta{ property: "twitter:description", content: plain_text(@conference.description) }
   - if @conference.picture?
     %meta{ property: "og:image", content: @image_url }
     %meta{ property: "og:image:secure_url", content: @image_url }