Here is the compled OEM module for MariaDB 10.3.9.
Because this version does not have some bug fixes I made here
but not yet released, discovery will not work, meaning that
the table columns must be manually declared.

The DLL must be placed in the plugin directory:
{MariaDB install dir}\lib\plugin

Also, Microsoft Casablanca, the cpprestsdk package,
must be installed (this I cannot do for you)
After installation, the directories containing the binary
of this package must be added to the PATH environment variable
and your machine be restarted after doing it.

If you don't know how to do it, ask the net; there are plenty
of site explaining how.

Here is an example of table declaration:

CREATE OR REPLACE TABLE webd (
  name char(6) DEFAULT NULL,
  country char(2) DEFAULT NULL,
  altitude char(1) DEFAULT NULL FIELD_FORMAT='location/@altitude',
  latitude char(7) DEFAULT NULL FIELD_FORMAT='location/@latitude',
  longitude char(8) DEFAULT NULL FIELD_FORMAT='location/@longitude',
  geobase char(8) DEFAULT NULL FIELD_FORMAT='location/@geobase',
  geobaseid char(7) DEFAULT NULL FIELD_FORMAT='location/@geobaseid',
  calctime char(6) DEFAULT NULL,
  sunrise char(19) DEFAULT NULL FIELD_FORMAT='@rise',
  sunset char(19) DEFAULT NULL FIELD_FORMAT='@set',
  time_from char(19) DEFAULT NULL FIELD_FORMAT='time/@from',
  time_to char(19) DEFAULT NULL FIELD_FORMAT='time/@to'
) ENGINE=CONNECT TABLE_TYPE=OEM  MODULE='Rest.dll' SUBTYPE=REST
FILE_NAME='weatherdata.xml'
CONNECTION='https://samples.openweathermap.org/data/2.5/forecast?q=London,us&mode=xml&appid=b6907d289e10d714a6e88b30761fae22'
OPTION_LIST='Ftype=XML';

(currently only XML, JSON and CSV file types are supported)

And executing:

select name, country, latitude, longitude from webd where name = 'LONDON';

Should reply:

+--------+---------+----------+-----------+
| name   | country | latitude | longitude |
+--------+---------+----------+-----------+
| London | US      | 39.8865  | -83.4483  |
+--------+---------+----------+-----------+

Defining the columns is exactly like if the table was file based.

If loading the module fails (saying no such file or directory)
or if an error occurs finding the GetREST function, let me know.
There are many reasons that can make all this to fail.
Instead of using JIRA, you can contact me at:

bertrandop@gmail.com

It will be faster with direct contact.

Enjoy and good luck!