Importers - Default to the current group when importing

Related issue (GitHub): #353936 (closed)

Problem to Solve

When importing a project by clicking the New project button, when I arrive on the page with the list of GitHub projects to select, the default group in the "To GitLab" column is my personal namespace and not the namespace of the group where I initiated the import flow.

This is confusing and it may lead to company projects being created in the employees' personal namespaces.

This flow can be observed in this video for GitHub importer but applies for all of them

Proposed Solution

Ensure we are correctly passing namespace_id as parameter to the status page of importer (frontend support for namespace_id is already there)