How to change Digest username in freepbx?

Question

linux

There is a trunk

type=peer
host=example.local
port=5060
fromuser=sip1
secret=pass
fromdomain=example1.local
insecure=port,invite
context=default
allow=all
nat=yes
qualify=yes

With a registration line:
[email protected]:[email protected]
There is also a line in sip_registrations_custom.conf
auth=sip2:[email protected]
No registration.
On the other side they say:

Authorization: Digest username="sip1", realm="BroadWorks", algorithm=MD5, uri="sip:example.local", nonce="BroadWorksXiobe3c3bTs6cwotBW", response="d9c9f97847975469107168ddf4cb3a23", qop=auth, cnonce="3175286b", nc=00000001
Expires: 120
Contact: <sip:[email protected]:5060>
Content-Length: 0

“In the highlighted red should be sip2 instead of sip1
Unfortunately, according to the FREEPBX settings, I can’t tell you where to edit it.”
Those. in other words - how to explicitly specify the Digest username?