improve: add documentation guidline for agents #6987

Job	Run time
sample_operators_tests (sample-operators/leader-election)	3m 14s
sample_operators_tests (sample-operators/tomcat-operator)	3m 5s
sample_operators_tests (sample-operators/operations)	8m 16s
sample_operators_tests (sample-operators/mysql-schema)	2m 33s
sample_operators_tests (sample-operators/webpage)	2m 40s
	19m 48s

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