FusionPBX/FreeSWITCH save CLID on transfer

Idea is when call is received, transfer to next destination should come with callerID was received originally, not updated in moment of transfer. Sometimes it's needed for correct CRM integration or peoples just get used to it, cause it's default with blind transfer.

Actually, same ideas that described here, but for use in FusionPBX.

1. Create context save_transfer with order ~85
condition - <empty>
action - export - nolocal:execute_on_answer_1=lua number_save_on_transfer_store.lua
action - export - api_hangup_hook=lua number_save_on_transfer_db_cleanup.lua

2. Create context restore_transfer with order higher, than save_trasfer, ~80
condition - ${db(exists/number_transfer_store/${sip_from_user})} - ^true$
action - set - restored_number_on_transfer=${db(select/number_transfer_store/${sip_from_user})} - inline
action - set - effective_caller_id_number=${restored_number_on_transfer}
action - set - effective_caller_id_name=${restored_number_on_transfer}
action - db - delete/number_transfer_store/${sip_from_user}
condition - ${db(exists/number_transfer_store/${sip_from_user}_name)} - ^true$
action - set - restored_number_on_transfer_name=${db(select/number_transfer_store/${sip_from_user}_name)} - inline
action - set  - effective_caller_id_name=${restored_number_on_transfer_name}
action - db - delete/number_transfer_store/${sip_from_user}_name

Lua files:
/usr/share/freeswitch/scripts/number_save_on_transfer_store.lua

-- Save number_answered / original caller_id to database

--api = freeswitch.API()

if (session:ready()) then
    answered_extension = session:getVariable("dialed_user")

    caller_id = session:getVariable("restored_number_on_transfer")
    caller_name = session:getVariable("restored_number_on_transfer_name")

    if (caller_id == nil) then
        caller_id = session:getVariable("sip_from_user")
    end
    if (caller_name == nil) then
        caller_name = session:getVariable("sip_from_display")
    end
    if (answered_extension ~= nil and caller_id ~= nil) then
        freeswitch.consoleLog("INFO", "[NUMBER_ON_TRANSFER_SAVE] Got answered call from "..caller_id.." to "..answered_extension.."\n")
        session:execute('db', 'insert/number_transfer_store/'..answered_extension..'/'..caller_id)
        if (caller_name ~= nil) then
            session:execute('db', 'insert/number_transfer_store/'..answered_extension..'_name/'..caller_name)
        end
    end
end

/usr/share/freeswitch/scripts/number_save_on_transfer_db_cleanup.lua

-- Cleanup database

api = freeswitch.API()
sip_to_user = env:getHeader("variable_last_sent_callee_id_number")

if (sip_to_user ~= nil) then
--serialized = env:serialize()
--freeswitch.consoleLog("INFO","[hangup]\n" .. serialized .. "\n")

    freeswitch.consoleLog("INFO", "[DB_CLEANUP] Cleaning " .. sip_to_user .. "\n")
    api:executeString('db delete/number_transfer_store/'..sip_to_user)
    api:executeString('db delete/number_transfer_store/'..sip_to_user..'_name')
end



P.S.: At the end, db is can be easily replaced with hash. As we don't need persistence storage here.