Do PL/pgSQL support to create a function to make HTTP request. We have a requirement to send data to external server from Postgres DB using HTTP/HTTPS Post Method.
Surely It doesn't support it. You can use some untrusted language - but it is not safe.
you can use https://github.com/pramsey/pgsql-http extension. It is much better, but still it not good idea. Stored procedures are perfect for work inside database. Communication with outer world is not good
a) outer world is not transactional
b) outer world is too slow.
This is task for application (communication) server.