Client construction settings consumed by the lazy SDK arm.
readonly
projectId: string
The GCP project the instance lives in.
readonly
optional
apiEndpoint: string
An explicit API endpoint, such as 127.0.0.1:8086 for cbtemulator.
Measured: an endpoint alone reaches the emulator with no
BIGTABLE_EMULATOR_HOST and no credentials, which is why the adapter
takes it as an option rather than reading the environment.