app: Add CoAP client AT commands

Add AT#XCOAPCREQ, AT#XCOAPCCANCEL, and AT#XCOAPCDATA to drive Zephyr
coap_client over a connected UDP/DTLS socket. Responses are delivered
asynchronously via #XCOAPCDATA / #XCOAPCHEAD and #XCOAPCSTAT URCs.

Jira: SM-225

Signed-off-by: Juha Ylinen <juha.ylinen@nordicsemi.no>

Author: juhaylinen

app/CMakeLists.txt

@@ -29,6 +29,7 @@ target_sources_ifdef(CONFIG_SM_CMUX app PRIVATE src/sm_cmux.c)
 target_sources_ifdef(CONFIG_SM_GNSS app PRIVATE src/sm_at_gnss.c)
 target_sources_ifdef(CONFIG_SM_NRF_CLOUD app PRIVATE src/sm_at_nrfcloud.c)
 target_sources_ifdef(CONFIG_SM_MQTTC app PRIVATE src/sm_at_mqtt.c)
+target_sources_ifdef(CONFIG_SM_COAPC app PRIVATE src/sm_at_coap.c)
 target_sources_ifdef(CONFIG_SM_HTTPC app PRIVATE src/sm_at_httpc.c)
 target_sources_ifdef(CONFIG_SM_MODEM_TRACE_BACKEND_CMUX app PRIVATE src/sm_trace_backend_cmux.c)
 target_sources_ifdef(CONFIG_SM_MODEM_TRACE_BACKEND_UART app PRIVATE src/sm_trace_backend_uart.c)

app/Kconfig

@@ -266,6 +266,15 @@ config SM_NRF_CLOUD_LOCATION
 	  Enable the nRF Cloud Location service for cloud-assisted geolocation.
 	  Supports cellular and Wi-Fi positioning.
 
+config SM_COAPC
+	bool "CoAP client support"
+	default y
+	select COAP
+	select COAP_CLIENT
+	select EXPERIMENTAL
+	help
+	  Enable CoAP client AT commands for making CoAP requests.
+
 config SM_MQTTC
 	bool "MQTT client support"
 	default y

app/overlay-nrf-device-provisioning.conf

@@ -12,6 +12,10 @@ CONFIG_NRF_PROVISIONING_ROOT_CA_SEC_TAG=42384
 CONFIG_NRF_PROVISIONING_PROVIDE_ATTESTATION_TOKEN=y
 CONFIG_NRF_PROVISIONING_LOG_LEVEL_INF=y
 
+# Three concurrent CoAP client instances are required: one for nRF Device Provisioning,
+# one for AT#XCOAPCREQ requests, and one for AT#XNRFCLOUD CoAP-based cloud communication.
+CONFIG_COAP_CLIENT_MAX_INSTANCES=3
+
 # Timeout for waiting for the modem to enter the desired connectivity state during provisioning.
 CONFIG_NRF_PROVISIONING_MODEM_STATE_WAIT_TIMEOUT_SECONDS=120