The limitation is in SQL. I’m surprised to learn this changed between versions 14 and 15, but will accept the claim without verifying. From the maria prompt:
MariaDB [asterisk]> describe incoming;
+-----------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+--------------+------+-----+---------+-------+
| cidnum | varchar(20) | YES | | NULL | |
| extension | varchar(50) | NO | | NULL | |
*snip*
You can manually alter the type to accpet 50 chars with the following:
MariaDB [asterisk]> ALTER TABLE incoming MODIFY COLUMN cidnum varchar(50) NULL;
Query OK, 1 row affected (0.02 sec)
Records: 1 Duplicates: 0 Warnings: 0
MariaDB [asterisk]> describe incoming;
+-----------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+--------------+------+-----+---------+-------+
| cidnum | varchar(50) | YES | | NULL | |
| extension | varchar(50) | NO | | NULL | |
*snip*
This is a work around, a feature request (or ideally a pull request) is the way to get it fixed for everyone. https://issues.freepbx.org/