Create API key

Create a new API key for the authenticated user.

The full key value is returned only once in the creation response and cannot be retrieved again afterwards.

expires_at is required:

• A future datetime expires the key at that time.
• null creates a key that never expires.

Workspace scoping (optional): include scopes — a list of {workspace_id, permission} entries — to restrict the key to those workspaces. Each entry's permission is one of viewer, editor, or owner, and cannot exceed the role you currently hold on that workspace; a 400 is returned otherwise. Different scopes on the same key can carry different permissions.