improve: add license headers to source files #5604

Job	Run time
check_format_and_unit_tests	2m 47s
build / Special integration tests (24)	2m 16s
build / Special integration tests (21)	3m 0s
build / Special integration tests (17)	2m 28s
build / httpclient-tests (jdk) / Integration tests (24, 1.32.0, jdk)	7m 21s
build / httpclient-tests (jetty) / Integration tests (24, 1.32.0, jetty)	7m 20s
build / httpclient-tests (vertx) / Integration tests (24, 1.32.0, vertx)	7m 20s
build / integration_tests (17, 1.32.4) / Integration tests (17, 1.32.4, vertx)	7m 21s
build / integration_tests (21, 1.30.12) / Integration tests (21, 1.30.12, vertx)	7m 22s
build / integration_tests (17, 1.33.1) / Integration tests (17, 1.33.1, vertx)	7m 19s
build / integration_tests (24, 1.30.12) / Integration tests (24, 1.30.12, vertx)	7m 20s
build / integration_tests (21, 1.32.4) / Integration tests (21, 1.32.4, vertx)	7m 19s
build / integration_tests (21, 1.31.8) / Integration tests (21, 1.31.8, vertx)	7m 22s
build / integration_tests (17, 1.30.12) / Integration tests (17, 1.30.12, vertx)	7m 21s
build / integration_tests (21, 1.33.1) / Integration tests (21, 1.33.1, vertx)	7m 22s
build / integration_tests (24, 1.31.8) / Integration tests (24, 1.31.8, vertx)	7m 21s
build / integration_tests (24, 1.33.1) / Integration tests (24, 1.33.1, vertx)	7m 17s
build / integration_tests (24, 1.32.4) / Integration tests (24, 1.32.4, vertx)	7m 21s
build / integration_tests (17, 1.31.8) / Integration tests (17, 1.31.8, vertx)	7m 19s
	2h 0m 36s

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