Description of the problem, including code/CLI snippet

GitLab v3/v4 API support numeric project id and project path as arguments but seems the python-gitlab support only numeric argument with exception of the project command.

Expected Behavior

Without having to create two roundtrips (or implement caching), I would expect the CLI API also support project name as project id argument.

Perhaps the project_id parameter is not properly urlencoded?

Actual Behavior

$ gitlab project get --id=group-name/project-name
id: 813
path: project-name

➔ gitlab project get --id=813
id: 813
path: project-name

➔ gitlab project-variable list --project-id=813
key: MYSQL_PASSWORD

➔ gitlab project-variable list --project-id=group-name/project-name
Impossible to list objects (404: 404 Not Found)

Specifications

• python-gitlab version: 1.8.0
• API version you are using (v3/v4): v4
• Gitlab server version (or gitlab.com): 11.10.4