TEL-6718: Fix transfer_extension CRIT log spam in switch_channel.c:1580

[minhtuan1407-telnyx]

Summary

Fixes TEL-6718 — [CRIT] switch_channel.c:1580 Invalid data (${transfer_extension} contains a variable) log spam.

Root Cause

Commit 6d3c0eaf7c (ENGDESK-43915: Fire FS Events for IVR Transfer) added transfer tracking variables in switch_ivr_session_transfer() using switch_channel_set_variable(), which defaults to var_check=SWITCH_TRUE.

When extension contains unexpanded FreeSWITCH ${...} references (legitimately passed via ESL uuid_transfer), switch_string_var_check_const() detects ${ and emits the CRIT at switch_channel.c:1580.

Fix

Change the transfer tracking variable writes to use switch_channel_set_variable_var_check(..., SWITCH_FALSE) so the metadata is stored as-is:

switch_channel_set_variable_var_check(channel, "transfer_extension", extension, SWITCH_FALSE);
switch_channel_set_variable_var_check(channel, "transfer_dialplan", use_dialplan, SWITCH_FALSE);
switch_channel_set_variable_var_check(channel, "transfer_context", use_context, SWITCH_FALSE);

Why this is safe

• These are informational transfer-tracking values, not values that need validation/expansion.
• SWITCH_TRANSFER_SOURCE_VARIABLE already uses SWITCH_FALSE in the same function.
• This prevents false-positive CRITs without changing transfer behavior.

Test Plan

1. Trigger uuid_transfer with an extension containing ${var}.
2. Verify no CRIT at switch_channel.c:1580.
3. Verify transfer events still contain Transfer-Extension, Transfer-Dialplan, and Transfer-Context.
4. Verify normal transfers remain unchanged.

— 🦀 Analysis by Council of Claws (Dev, Orchestrator)