feat: add quarantine button on project details

A button that re-uses the malware routes.
We can create bespoke routes and views for quarantine manipulation if we
find that using this feature leads to confusing redirects, but for now
I'm opting for simpler implementation.

Signed-off-by: Mike Fiedler <miketheman@gmail.com>

warehouse/admin/templates/admin/projects/delete.html

@@ -19,7 +19,7 @@
 
   <div class="card card-danger collapsed-card">
     <div class="card-header">
-      <h3 class="card-title">Delete Project</h3>
+      <h3 class="card-title">Delete / Quarantine Project</h3>
       <div class="card-tools">
         <button type="button" class="btn btn-tool" data-card-widget="collapse"><i class="fas fa-plus"></i></button>
       </div>
@@ -29,6 +29,7 @@ <h3 class="card-title">Delete Project</h3>
       <p>
         Deleting will irreversibly delete this project along with
         <a href="{{ request.route_path('admin.project.releases', project_name=project_name) }}">{{ project.releases|length() }} releases</a>.
+        Consider Quarantine if you want to keep the project but make it unavailable.
       </p>
       <div class="form-group col-sm-12">
         <label for="confirm_project_name">
@@ -39,9 +40,49 @@ <h3 class="card-title">Delete Project</h3>
     </div>
 
     <div class="card-footer">
+      <div class="float-left">
+        <button type="button"
+                class="btn btn-block btn-outline-warning"
+                data-toggle="modal"
+                data-target="#modal-quarantine">Quarantine Project</button>
+      </div>
       <div class="float-right">
         <button type="submit" class="btn btn-primary" title="{{ 'Deleting requires superuser privileges' if not request.has_permission(Permissions.AdminProjectsDelete) }}" {{ "disabled" if not request.has_permission(Permissions.AdminProjectsDelete) }}>Confirm</button>
       </div>
     </div>
   </div>
 </form>
+
+<div class="modal fade" id="modal-quarantine">
+  <div class="modal-dialog modal-quarantine">
+    <form id="quarantine"
+          action="{{ request.route_path('admin.malware_reports.project.verdict_quarantine', project_name=project_name) }}"
+          method="post">
+      <input name="csrf_token"
+             type="hidden"
+             value="{{ request.session.get_csrf_token() }}">
+      <div class="modal-content">
+        <div class="modal-header bg-warning">
+          <h4 class="modal-title">Quarantine Project</h4>
+          <button type="button" class="close" data-dismiss="modal" aria-label="Close">
+            <span aria-hidden="true">×</span>
+          </button>
+        </div>
+        <div class="modal-body">
+          <p>
+            Confirming that <code>{{ project_name }}</code> needs further examination.
+          </p>
+          <p>
+            This will remove the Project from being installable,
+            and prohibit the Project from being changed by the Owner.
+          </p>
+        </div>
+        <div class="modal-footer justify-content-between">
+          <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
+          <button type="submit" class="btn btn-warning">Verdict: Quarantine Project</button>
+        </div>
+      </div>
+    </form>
+  </div>
+</div>
+<!-- /.modal -->