add external handling #1692

Job	Run time
Smoke test - core, schema (18.x)	1m 39s
Lint	32s
Smoke test - core, schema (20.x)	1m 36s
Smoke test - cli (macos-latest, 18.x)	2m 20s
Test - cli (macos-latest, 18.x)	1m 6s
Smoke test - cli (macos-latest, 20.x)	2m 19s
Test - cli (macos-latest, 20.x)	1m 17s
Test - core, schema, legacy-scripting-runner (18.x)	1m 2s
Smoke test - cli (ubuntu-latest, 18.x)	2m 35s
Test - cli (ubuntu-latest, 18.x)	47s
Smoke test - cli (ubuntu-latest, 20.x)	2m 0s
Test - schema-to-ts	32s
Test - core, schema, legacy-scripting-runner (20.x)	1m 15s
Test - cli (ubuntu-latest, 20.x)	48s
	19m 48s

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