Stasis: Convey transfer information to applications

This fixes a class of issues where Stasis applications were not made
aware that their channels were being manipulated or replaced by
external entitiessuch as transfers, AMI commands, or dialplan
applications such as Bridge(). Inconsistent information such as
StasisEnd events with unknown channels as a result of masquerades has
also been corrected. To accomplish these fixes, several new fields
were added to blind and attended transfer messages as well as
StasisStart and BridgeAttendedTransfer Stasis events.

ASTERISK-23941 #close
Review: https://reviewboard.asterisk.org/r/3865/
Review: https://reviewboard.asterisk.org/r/3857/
Review: https://reviewboard.asterisk.org/r/3852/
Review: https://reviewboard.asterisk.org/r/3816/
Review: https://reviewboard.asterisk.org/r/3731/
Review: https://reviewboard.asterisk.org/r/3729/
Review: https://reviewboard.asterisk.org/r/3728/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@420325 65c4cc65-6c06-0410-ace0-fbb531ad65f3

rest-api/api-docs/events.json

@@ -285,6 +285,11 @@
 					"required": true,
 					"type": "Channel"
 				},
+				"transferee": {
+					"description": "The channel that is being transferred",
+					"required": false,
+					"type": "Channel"
+				},
 				"exten": {
 					"description": "The extension transferred to",
 					"required": true,
@@ -325,6 +330,21 @@
 					"required": true,
 					"type": "Channel"
 				},
+				"replace_channel": {
+					"description": "The channel that is replacing transferer_first_leg in the swap",
+					"required": false,
+					"type": "Channel"
+				},
+				"transferee": {
+					"description": "The channel that is being transferred",
+					"required": false,
+					"type": "Channel"
+				},
+				"transfer_target": {
+					"description": "The channel that is being transferred to",
+					"required": false,
+					"type": "Channel"
+				},
 				"result": {
 					"description": "The result of the transfer attempt",
 					"required": true,
@@ -670,6 +690,10 @@
 				"channel": {
 					"required": true,
 					"type": "Channel"
+				},
+				"replace_channel": {
+					"required": false,
+					"type": "Channel"
 				}
 			}
 		},