DAST On-demand scans MVC - Initiate Scan - Create form - Frontend

• Related issue: #218683 (closed)

What does this MR do?

This adds the actual form for running on-demand passive DAST scan against a given target URL.

In this iteration, clicking on the empty state's primary button in the On-demand scans page opens up a form for initiating a new scan.

The target URL currently is the only editable field. In the future, we will provide more options for selecting the pipeline's attached branch, as well different scan modes.

When the form is submitted, and if the pipeline was successfully initiated, the user is redirected to the pipeline's page.

Screenshots

State	Preview
At rest
Scan mode tooltip
Attached branch tooltip
Target URL tooltip
Invalid target URL
Valid target URL
Submitted
Submission failed
At rest (mobile)

Recording

on_demand_scans_recording

How to test this?

• Enable the security_on_demand_scans_feature_flag feature flag:

echo "Feature.enable(:security_on_demand_scans_feature_flag)" | spring rails c

• Navigate to the On-demand scans page in some project: <group>/<project>/-/on_demand_scans

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry (behind a feature flag)
• [-] Documentation (if required) (see #218686 (closed))
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done