Ensure HasWiki constructs wikis with users as owners

What does this MR do?

This MR fixes a ~bug whereby HasWiki#wiki constructs wikis that cannot save their pages.

Generally this does not affect our controllers, since they build wikis with the current user.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• 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