Direct Transfer should respect group membership lock

What does this MR do and why?

This one is slightly different to the MRs for file-based and GitHub import because of the way Direct Transfer handles group import.

project#membership_locked? returns true if the restriction is in place on the direct parent of the project.

Group
┗ Project
  ┗ Member

DestinationGroup
┗ Group
  ┗ Project
  ┗ Member

So for group import, it's kind of irrelevant: membership only seems to be created on the group anyway, and that's unaffected by this setting.

This MR does however still apply when using the DT API to import a project entity directly.

curl --request POST \
  --url "http://gdk.test:3000/api/v4/bulk_imports" \
  --header "content-type: application/json" \
  --header "PRIVATE-TOKEN: $GITLAB_DEV_TOKEN" \
  --data "{
    \"configuration\": {
      \"url\": \"http://gdk.test:3000\",
      \"access_token\": \"$GITLAB_DEV_TOKEN\"
    },
    \"entities\": [
      {
        \"source_full_path\": \"nested-lock/next-level/nested-lock-project\",
        \"source_type\": \"project_entity\",
        \"destination_slug\": \"imported-project\",
        \"destination_namespace\": \"dest-namespace\",
        \"migrate_projects\": true
      }
    ]
  }"

In this case, we would still expect the destination group setting to be respected.

References

#559224

How to set up and validate locally

1. Create a destination group and disable direct project memberships.
   • /groups/example-group/-/edit#js-permissions-settings
2. Import a project directly into the group using the Direct Transfer API.

   curl --request POST \
     --url "http://gdk.test:3000/api/v4/bulk_imports" \
     --header "content-type: application/json" \
     --header "PRIVATE-TOKEN: $GITLAB_DEV_TOKEN" \
     --data "{
       \"configuration\": {
         \"url\": \"http://gdk.test:3000\",
         \"access_token\": \"$GITLAB_DEV_TOKEN\"
       },
       \"entities\": [
         {
           \"source_full_path\": \"source-group/source-project\",
           \"source_type\": \"project_entity\",
           \"destination_slug\": \"imported-project-001\",
           \"destination_namespace\": \"example-group\",
           \"migrate_projects\": true
         }
       ]
     }"

3. Verify the following:
   1. The tracker is marked as skipped.
   2. No direct membership should be created on the project.
   3. A log entry should be created in log/exporter.log

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