Refactor removing user from group

Instead of generating html code for each modal that asks for removing
a user from a group only one modal is created. Arguments for the modal
are passed with "data-*" attributes.

Rename the modal and the partials from "remove" to "delete", for being
consistent with the naming of the previous modals and partials.

src/api/app/views/webui2/shared/_group_members_table.html.haml

@@ -11,9 +11,9 @@
             %td= link_to(user, user_show_path(user))
             %td.text-nowrap
               - if policy(group).update?
-                = link_to('#', data: { toggle: 'modal', target: "#delete-group-user-#{user.id}-modal" }) do
+                = link_to('#', data: { toggle: 'modal', target: '#delete-group-user-modal', user: user.to_s,
+                  action: group_user_delete_path(group, user) }) do
                   %i.fas.fa-times-circle.text-danger{ title: "Remove user '#{user}' from '#{group}' group." }
-                = render(partial: 'remove_user_modal', locals: { group: group, user: user })
       - else
         %tr
           %td{ colspan: 2 } This group does not contain users.
@@ -22,3 +22,4 @@
       %i.fas.fa-plus-circle.text-primary
       Add User
     = render(partial: 'add_user_modal', locals: { group: group })
+    = render(partial: 'delete_group_user_modal', locals: { group: group })

src/api/app/views/webui2/webui/groups/_delete_group_user_modal.html.haml

@@ -0,0 +1,27 @@
+.modal.fade{ id: 'delete-group-user-modal', tabindex: -1, role: 'dialog', aria: { labelledby: 'delete-modal-label', hidden: true } }
+  .modal-dialog.modal-dialog-centered{ role: 'document' }
+    .modal-content
+      .modal-header
+        %h5.modal-title
+          Remove user
+          = succeed '?' do
+            = surround "'" do
+              %span.user
+      .modal-body
+        %p
+          Please confirm removing user
+          = surround "'" do
+            %span.user
+          from group '#{group}'.
+        = form_tag(nil, method: :delete) do
+          .modal-footer
+            %button.btn.btn-sm.btn-outline-secondary.px-4{ data: { dismiss: 'modal' } }
+              Cancel
+            = submit_tag('Delete', class: 'btn btn-sm btn-danger px-4')
+= content_for :ready_function do
+  :plain
+    $('#delete-group-user-modal').on('show.bs.modal', function (event) {
+      var link = $(event.relatedTarget);
+      $(this).find('.user').text(link.data('user'));
+      $(this).find('form').attr('action', link.data('action'));
+    });