Use runner for DAST Site Validation

What does this MR do?

this merge request adds the ability to validate a dast site for active scans using the runner rather than using a sidekiq worker. the rationale behind this is that we wanted to give customers the ability to validate sites that may inaccessible from their gitlab instance but accessible from their runners. it may be enabled with the feature flag dast_runner_site_validation.

Notes

this feature will have accompanying documentation in the merge request that enables the feature flag by default.

Related Issue(s)

• #324990 (closed)
• #270751 (closed)

Manual QA

Template

you'll see that the job runs the container script correctly but it fails. this is because there's a bug in the api that's fixed in this merge request.

• project
• pipeline
• job

Feature

• enable feature flag Feature.enable(:dast_runner_site_validation)
• create a project
• create a dast site profile
• validate your dast site profile

Screenshots

Happy Path

Sad Path

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team