MT#61372 add alternative spellings

for `SIP message type` and add it to docs.

Change-Id: I1c674da227186067244912c88417be3bb9a9093a
(cherry picked from commit 8f458d0511)

daemon/call_interfaces.c

@@ -1909,13 +1909,25 @@ void call_ng_main_flags(sdp_ng_flags *out, str *key, bencode_item_t *value,
 			break;
 		case CSH_LOOKUP("sip-message-type"):
 		case CSH_LOOKUP("sip_message_type"):
+		case CSH_LOOKUP("SIP-message-type"):
+		case CSH_LOOKUP("SIP_message_type"):
 			switch (__csh_lookup(&s)) {
+				case CSH_LOOKUP("request"):
 				case CSH_LOOKUP("sip-request"):
 				case CSH_LOOKUP("sip_request"):
+				case CSH_LOOKUP("SIP-request"):
+				case CSH_LOOKUP("SIP_request"):
 					out->message_type = SIP_REQUEST;
 					break;
+				case CSH_LOOKUP("reply"):
+				case CSH_LOOKUP("sip-response"):
+				case CSH_LOOKUP("sip_response"):
+				case CSH_LOOKUP("SIP-response"):
+				case CSH_LOOKUP("SIP_response"):
 				case CSH_LOOKUP("sip-reply"):
 				case CSH_LOOKUP("sip_reply"):
+				case CSH_LOOKUP("SIP-reply"):
+				case CSH_LOOKUP("SIP_reply"):
 					out->message_type = SIP_REPLY;
 					break;
 				default:

docs/ng_control_protocol.md

@@ -568,6 +568,11 @@ Optionally included keys are:
 		Reject rtcp-mux if it has been offered. Can be used together with `offer` to achieve the opposite
 		effect of `demux`.
 
+* `SIP message type`
+
+    Contains a string indicating whether the SIP message that triggered this
+    signalling message was either a `SIP request` or a `SIP response`.
+
 * `via-branch`
 
 	The SIP `Via` branch as string. Used to additionally refine the matching logic between media streams