Possible ways to access runtime. Authentication mode.
Currently supports: Single User only.
Values:
RUNTIME_ACCESS_TYPE_UNSPECIFIED (0):
Unspecified access.
SINGLE_USER (1):
Single user login.
SERVICE_ACCOUNT (2):
Service Account mode.
In Service Account mode, Runtime creator will
specify a SA that exists in the consumer
project. Using Runtime Service Account field.
Users accessing the Runtime need ActAs (Service
Account User) permission.