user under project permissions with admin access can create a repository but cannot fork a repository into the project

Issue Summary

Users under project permissions with admin access within a specific user group can create a repository but cannot fork a repository into the project.

This links to the "Can create repositories for this workspace" option is disabled for the user group, but enabling this option allows forking to work within the project.

Steps to Reproduce

1. Create a user group and uncheck "Can create repositories for this workspace".
2. Add a user to the group
3. Add the group to a project with "Admin" permissions or add the user directly to the project with "Admin" permissions
4. The user forks a repository into the project they administer.

Expected Results

The user should be able to fork the repository to a project they administer 

Actual Results

The user can create a repository, but forking the repository fails with 

Error: "You can't create repositories under this account. You must specify an owner."

or

You do not have sufficient permissions to create repositories in this project/workspace. You must specify an owner."

Workaround

• Give the workspace group or add the user to a workspace group with "Can create projects in this workspace" permission

UPDATE: Organisations that are making use of the unified user management experience cannot apply the above workaround as these options are no longer available in group settings (as these are managed with roles in Atlassian admin). Only users with Product Admin role will be able to perform forks until this bug is resolved.