Persist On-demand Scans form values in localStorage

Implements #293844 (closed)

What does this MR do?

This MR uses LocalStorageSync component to persist On-demand scans form values.

• Cleans storage on successful form submissions
• Skips restoring from local storage while editing a form

Note: The changes are behind the feature flag dast_saved_scans.

Demo

on-demand-scan-persist720

Please note that the current demo clears the storage on failed form submissions as well, which is just for testing purposes.

How to test this?

1. Enable the :dast_saved_scans feature flag.

echo "Feature.disable(:dast_saved_scans)" | rails c

2. Navigate to the DAST scans management page at /:namespace/:project/-/on_demand_scans/new

3. Add this line to clear storage on form submits even when it fails

diff --git a/ee/app/assets/javascripts/on_demand_scans/components/on_demand_scans_form.vue b/ee/app/assets/javascripts/on_demand_scans/components/on_demand_scans_form.vue
index 7b611e5a4e3..336aede5cb8 100644
--- a/ee/app/assets/javascripts/on_demand_scans/components/on_demand_scans_form.vue
+++ b/ee/app/assets/javascripts/on_demand_scans/components/on_demand_scans_form.vue
@@ -314,6 +314,7 @@ export default {
       this.errorType = errorType;
       this.errors = errors;
       this.showAlert = true;
+      this.clearStorage = true; // Todo: Remove this, it's only for testing purposess
     },
     hideErrors() {
       this.errorType = null;

4. Fill out the form and reload the page