Create an API token

OAuth2 Client Credentials grant. Returns a Bearer access token.

Regular clients: token is scoped to the client's account — no additional parameters needed.

Super-user clients (account_id 10000): two options:

• Pass account_guid in the request body to receive a token scoped to that specific campaign account.
• Omit account_guid to receive an unscoped super-user token (scope: super). All subsequent requests using this token must include an X-Account-GUID header with the target campaign account GUID.