add api spec for feature flags allocations and exposure schedules endpoints #17336

Job	Run time
pre-commit / pre-commit	1m 7s
test / test (3.2, ubuntu-latest)	1m 8s
examples / examples	2m 32s
test / test (2.7, ubuntu-latest)	1m 45s
test / test (jruby-9.4.12.0, ubuntu-latest)	3m 36s
report	7s
	10m 15s

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