Changes to Send Reminder

added the non-success response with the status 429

the code response's property type changed from no type to string for status 403

the code response's property type changed from no type to string for status 404

the endpoint scheme security ApiKeyAuth was added to the API

the endpoint scheme security PermissionAuthenticationRequirement was removed from the API

api tag Subscribers added

added the non-success response with the status 401

the endpoint scheme security PermissionAuthenticationRequirement was added to the API

the endpoint scheme security AuthenticationRequirement was removed from the API

added the non-success response with the status 404