Add example / implementation for coap-handler #433

Job	Run time
check-style	17s
unit-tests (crypto-hacspec, ead-none)	1m 7s
unit-tests (crypto-hacspec, ead-zeroconf)	1m 5s
unit-tests (crypto-psa, ead-none)	1m 16s
unit-tests (crypto-psa, ead-zeroconf)	1m 6s
build-coap-example	57s
build-static-lib-and-headers (crypto-psa-baremetal)	1m 47s
build-edhoc-package (crypto-hacspec, ead-none)	2m 21s
build-example-for-cortex-m4 (crypto-psa, ead-none)	1m 15s
build-static-lib-and-headers (crypto-cryptocell310)	1m 7s
build-edhoc-package (crypto-hacspec, ead-zeroconf)	1m 8s
build-example-for-cortex-m4 (crypto-psa, ead-zeroconf)	2m 9s
build-edhoc-package (crypto-psa, ead-none)	1m 39s
generate-fstar	0s
build-example-for-cortex-m4 (crypto-cryptocell310, ead-none)	2m 5s
run-example-on-qemu (crypto-psa, ead-none)	1m 25s
build-edhoc-package (crypto-psa, ead-zeroconf)	2m 34s
build-example-for-cortex-m4 (crypto-cryptocell310, ead-zeroconf)	58s
build-edhoc-package (crypto-psa-baremetal, ead-none)	1m 9s
run-example-on-qemu (crypto-psa, ead-zeroconf)	2m 27s
build-edhoc-package (crypto-psa-baremetal, ead-zeroconf)	1m 45s
build-edhoc-package (crypto-cryptocell310, ead-none)	1m 59s
build-edhoc-package (crypto-cryptocell310, ead-zeroconf)	2m 7s
release	0s
	33m 43s

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