Add contest param for offline form participation

app/views/contests/_form.html.slim

@@ -15,6 +15,11 @@ h4.mt-5 = t("contests.form.general")
       .form-check.form-switch
         = form.check_box :public, class: "form-check-input"
         = form.label :public
+  .row.mb-3
+    .col
+      .form-check.form-switch
+        = form.check_box :offline_form, class: "form-check-input"
+        = form.label :offline_form
   .row.mb-3
     .col
       .form-check.form-switch

app/views/contests/show.html.slim

@@ -20,6 +20,12 @@ javascript:
     - else
       a.btn.btn-success.disabled
         = t("contests.show.public_scoreboard_disabled")
+    - if @contest.offline_form
+      a.ms-3.btn.btn-success href="/public/#{@contest.slug}/offline"
+        = t("contests.show.open_offline_form")
+    - else
+      a.ms-3.btn.btn-success.disabled
+        = t("contests.show.offline_form_disabled")
     button.btn.btn-success.ms-3 onclick="copyExtensionUrlToClipboard()"
       css:
         button > svg {