Your app signs users in with Google, Azure AD or AWS Cognito and sends the token it gets to API Maker.
API Maker checks the token with the keys of the provider, finds the user in a table of yours, and runs the call with the groups of that user.
Send the token in its header: x-google-authorization, x-azure-authorization or x-aws-authorization.
Read the opened token in your code from g.req.auth.authGoogle, g.req.auth.authAzure or g.req.auth.authAWS.
For any other system, write a custom provider: a token generator and a token validator in TypeScript. Send its token in x-custom-authorization and read the result in g.req.auth.authCustom.