Add. BLF indication for call forward. (#2664)

* Add. BLF indication for call forward.

To display general status of CallForward use blf like `forward+<extension>`
To display status for specific phone number use blf like `forward+<extension>/<number>`

* Fix. Escape variable in regex expression.

* Fix. Sync DND and CF blf.

* Add. `blf_subscribe` service which can handle all custom subscriptions.

To run for specific protocol it possible run as `luarun blf_subscribe.lua <PROTO>`

resources/install/scripts/resources/functions/blf.lua

@@ -0,0 +1,46 @@
+local presence_in   = require "resources.functions.presence_in"
+
+local function blf(enabled, proto, id, domain)
+	local user = string.format('%s+%s@%s', proto, id, domain)
+	presence_in.turn_lamp(enabled, user)
+end
+
+local function dnd(enabled, extension, number_alias, domain)
+	blf(enabled, 'dnd', extension, domain)
+	if number_alias and #number_alias > 0 then
+		blf(enabled, 'dnd', number_alias, domain)
+	end
+end
+
+local function forward(enabled, extension, number_alias, number, domain)
+	if number then
+		extension = extension .. '/' .. number
+		if number_alias and #number_alias > 0 then
+			number_alias = number_alias .. '/' .. number
+		end
+	end
+	blf(enabled, 'forward', extension, domain)
+	if number_alias and #number_alias > 0 then
+		blf(enabled, 'forward', number_alias, domain)
+	end
+end
+
+local function forward_toggle(enabled, extension, number_alias, old_number, new_number, domain)
+	-- turn off previews BLF number
+		if old_number and #old_number > 0 and old_number ~= new_number then
+			forward(false, extension, number_alias, old_number, domain)
+		end
+
+	-- set common BLF status
+		forward(enabled, extension, number_alias, nil, domain)
+
+	-- set destination specifc status
+		if new_number and #new_number > 0 then
+			forward(enabled, extension, number_alias, new_number, domain)
+		end
+end
+
+return {
+	dnd = dnd;
+	forward = forward_toggle;
+}