Extracts the phone number from a SIP address header value — handles "Name" <sip:+1555@host>;tag=…, <sip:+1555@host>, sip:+1555@host, and tel:+1555. Returns the user part verbatim (keeping a leading +), or '' when no recognizable number is present.
"Name" <sip:+1555@host>;tag=…
<sip:+1555@host>
sip:+1555@host
tel:+1555
+
Extracts the phone number from a SIP address header value — handles
"Name" <sip:+1555@host>;tag=…,<sip:+1555@host>,sip:+1555@host, andtel:+1555. Returns the user part verbatim (keeping a leading+), or '' when no recognizable number is present.