BUG #17237: set_config: Custom parameter names must be two or more simple identifiers separated by dots.

The following bug has been logged on the website:

Bug reference:      17237
Logged by:          Alexey Stepanov
Email address:      stepaunov@gmail.com
PostgreSQL version: 14.0
Operating system:   Debian 8.3.0-6, 64-bit
Description:

Our app uses guids as first part of set_config parameter name.

On PostgreSQL 14.0 this script results in an error:
SELECT set_config('182e33e7-12ff-4c4f-bc6e-0822e72fa7a4.param1'
,'test',true);

Exception:
[42602] ERROR: invalid configuration parameter name
"182e33e7-12ff-4c4f-bc6e-0822e72fa7a4.param1"
Custom parameter names must be two or more simple identifiers separated by
dots.


On previous versions, for example, on PostgreSQL 12.1 on
x86_64-pc-linux-gnu, compiled by gcc (Debian 6.3.0-18+deb9u1) 6.3.0
20170516, 64-bit,
the same script executed succesfully and works properly.