Stub out DAST site profile creation mutation

What does this MR do?

stubs out the basic shap for the dast site profile creation mutation.

note that i've opted not generate the schema as part of this merge request. as a result, i've also opted to leave out request specs. this is because, in the interests of iteration and to get feedback early, i've chosen to split this change up over several merge requests.

Related Issue(s)

#225404 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry behind feature toggle
• Documentation (if required)
• 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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• 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