Leaflet-WFST | OGC WFS-T client layer for Leaflet | Map library

I am new to this domain of GeoInformation development. I am following the below pipeline architecture flow to achieve a GIS-based application problem.

PostGIS - GeoServer - Leaflet

I have set up my leaflet client application which composes tiles to a map. I am also using some leaflet plugins (like Draw, zoom) in order to give users the option to mark and to draw on the map.

I am able to draw and get the GeoJSON features of the drawn polygon as shown below:

I am stuck after this part of figuring how do I need to send the polygon request drawn and retrieve the polygon (which is saved) programmatically. I know the answer is WFS-T, but how do I use this in my raw code. Here is the raw code example:

Raw Code link: https://pastebin.com/wCAHxVc0Follow the link

References:

1. https://gis.stackexchange.com/questions/266402/save-leaflet-drawn-features-with-attributes-to-postgis

2. https://github.com/Flexberry/Leaflet-WFST