GitPod: use jdk17 #65

Job	Run time
app-frontend	1m 32s
app-backend	3m 23s
ws-backend-steps (00_initial)	59s
ws-backend	1m 25s
ws-frontend	55s
ws-backend-steps (01_schema)	1m 3s
ws-frontend-steps (01_initial_uebungen)	1m 33s
ws-frontend-steps (10_useQuery)	1m 5s
ws-backend-steps (10_handler-function)	1m 1s
ws-backend-steps (15_schema-mapping)	1m 34s
ws-frontend-steps (15_useQuery-fetchMore)	1m 4s
ws-backend-steps (17_mutations)	2m 0s
ws-frontend-steps (20_useMutation)	1m 5s
ws-backend-steps (18_subscriptions)	1m 3s
ws-frontend-steps (30_useQuery_subscribeToMore)	1m 11s
ws-backend-steps (20_dataloader)	1m 45s
ws-frontend-steps (80_complete)	1m 8s
ws-backend-steps (25_batchmapping)	1m 13s
ws-backend-steps (30_error_handling)	1m 0s
ws-backend-steps (40_security)	1m 2s
ws-backend-steps (50_test)	1m 32s
ws-backend-steps (70_complete)	1m 35s
	30m 8s

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