Create a new GitLab project via the REST API in a user's personal namespace or a group, with visibility, README initialization, and default branch options.

Documented steps

1. POST https://gitlab.example.com/api/v4/projects with a JSON body containing at least name or path (path is required if name is omitted and vice versa; path defaults to a lowercase-with-dashes version of name if omitted).
2. Set namespace_id to a group or subgroup ID to create the project inside that group; omit it to create in the authenticated user's personal namespace.
3. Set visibility to "private", "internal", or "public" to control project visibility.
4. Set initialize_with_readme: true to create the repository with an initial README.md commit; do not combine this with import_url.
5. Set default_branch (e.g. "main") to name the initial branch — this parameter has no effect unless initialize_with_readme is also true.
6. Send: curl --request POST --header "PRIVATE-TOKEN: <token>" --header "Content-Type: application/json" --data '{"name":"new_project","namespace_id":"42","initialize_with_readme":"true"}' --url "https://gitlab.example.com/api/v4/projects/"
7. Docs: https://docs.gitlab.com/api/projects/, https://docs.gitlab.com/user/permissions/