Add allow registration switch

app/views/contests/_form.html.slim

@@ -4,12 +4,19 @@
       .form-floating
         = form.text_field :name, autocomplete: "off", class: "form-control"
         = form.label :name, class: "required"
-  .row
+  .row.mb-3
     .col
       .form-check.form-switch
         = form.check_box :team, class: "form-check-input"
         = form.label :team
           | Team contest
         .form-text For registration and UI display purposes
-  div.mt-3
-    = form.submit submit_text, class: "btn btn-primary"
+  .row.mb-3
+    .col
+      .form-check.form-switch
+        = form.check_box :allow_registration, class: "form-check-input"
+        = form.label :allow_registration
+        .form-text Generates a registration form for this contest
+  .row
+    .col
+      = form.submit submit_text, class: "btn btn-primary"