issue when integrating postgrest with wso2 api manager

Question

I am trying to integrate postgrest api into WSO2 API Manager. GET, PUT, DELETE works fine, but POST is not work correctly inside API manager.

step 1:

For example,

I have a table named server and postgrest api for that table is, http://localhost:3000/server

step 2:

Create an API in WSO2 API manager with production endpoint as our postgrest api (http://localhost:3000/server). (Quick start guide)

step 3:

Access the POST API of API manager (GET API works correctly). You will get following error for that.

ERROR - ClientWorker Invalid URL received
java.net.MalformedURLException: no protocol: /server?feedurl=eq.https%3A%2F%2Fwww.opsfol.io%2Fnotifications%2F19E10D4D&hostname=eq.abc.example.com&hostvendorname=eq.7794&memory=eq.2048&notes=is.null&notificationsenabled=eq.test&operatingsystem=eq.Linux&organizationrole=eq.3451&serialnumber=eq.&servertype=eq.Cloud%20Virtual&signature=eq.&title=eq.arun%20test%20mrng2&totalharddiskspace=eq.80&uid

Request body is converted as query parameter and through a Invalid URL error.