Use `iam` instead of `externalServiceRegistration` #950

Job	Run time
setup-matrix	7s
run-integration-tests (./examples/app-with-on-behalf-of-auth)	3m 2s
run-integration-tests (./examples/datasource-http)	1m 16s
run-integration-tests (./examples/panel-visx)	1m 12s
run-integration-tests (./examples/panel-frame-select)	1m 7s
run-integration-tests (./examples/datasource-http-backend)	3m 16s
run-integration-tests (./examples/app-with-extension-point)	2m 28s
run-integration-tests (./examples/app-basic)	2m 57s
run-integration-tests (./examples/panel-flot)	1m 5s
run-integration-tests (./examples/panel-scatterplot)	1m 23s
run-integration-tests (./examples/app-with-extensions)	2m 49s
run-integration-tests (./examples/app-with-backend)	3m 6s
run-integration-tests (./examples/panel-datalinks)	2m 39s
run-integration-tests (./examples/app-with-scenes)	2m 55s
run-integration-tests (./examples/datasource-basic)	3m 51s
run-integration-tests (./examples/datasource-streaming-websocket/streaming-websocket-plugin)	1m 19s
run-integration-tests (./examples/app-with-dashboards)	2m 43s
run-integration-tests (./examples/datasource-logs)	1m 26s
run-integration-tests (./examples/panel-basic)	2m 50s
run-integration-tests (./examples/datasource-streaming-backend-websocket/streaming-backend-websoc...	2m 15s
run-integration-tests (./examples/app-with-service-account)	2m 59s
run-integration-tests (./examples/panel-plotly)	2m 49s
notify	0s
	49m 34s

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