It actually doesn't create neither database or property.

Check that %Service_DocDB is enabled. Your screenshot also shows that database gets created.

if I have 20 properties... this would be a long code

You need to cycle over all properties, so +2 lines probably.

Made an erro in URL, it's not  .../db/DBName/Propname but .../prop/db/DBName/Propname.

Here's a sample code that creates a db and a property.

import requests

def getBaseUrl(host = "127.0.0.1", port = 52773,  namespace = "user", db = "test"):
    return "http://{}:{}/api/docdb/v1/{}/db/{}" .format(*[host, port, namespace, db])

def getPropertyUrl(property, host = "127.0.0.1", port = 52773,  namespace = "user", db = "test"):
    return "http://{}:{}/api/docdb/v1/{}/prop/{}/{}" .format(*[host, port, namespace, db, property])

def main():

    url = getBaseUrl()
    print(url)
    header = {
        'Content-Type': 'application/json',
    }

    session = requests.Session()
    session.auth = ("_SYSTEM", "SYS")

    response = session.get(url, headers=header)
    #response = requests.get(url, headers=header)
    print(response.status_code)  # Number of error

    if response.status_code == 404:
        print('DB not found, create DB ...')
        response = session.post(url, headers=header)
        print(response.status_code)
    elif response.status_code != 200:
        print('Unknown error: ' + response.status_code + ' ' + response.reason)
    else:
        property = "Ergebniszuf"
        # check that property exist
        response = session.get(getPropertyUrl(property), headers=header)

        if response.status_code == 404:
            print('Property not found, creating property: ' + property)
            response = session.post(getPropertyUrl(property), params= {"type":"%Numeric", "path": property, "unique":0}, headers=header)
            print(response)
        elif response.status_code != 200:
            print('Unknown error: ' + response.status_code + ' ' + response.reason)
        else:

            print('DB found, load data...')

    return 1


if __name__ == '__main__':
    print(main())

2012.1.4 has JSON support via %ZEN.proxyObject

set obj = ##class(%ZEN.proxyObject).%New()
set obj.createTransactionRequest= ##class(%ZEN.proxyObject).%New()
set obj.createTransactionRequest.merchantAuthentication = ##class(%ZEN.proxyObject).%New()
set obj.createTransactionRequest.merchantAuthentication.name = "gfufet9QVgT5P"
do obj.%ToJSON()

Also you can use %ZEN.Auxiliary.jsonProvider to convert object into JSON.

Interesting. Check this article - I think you'll need either HTTP Debugging proxy (probably) or Packet analyzer (maybe) to debug this further.

As you have reference implementation (Postman) you can start by comparing Postman request/response and Ensemble request/response using HTTP Debugging proxy.

When you get sc=1 , what about:

set resp=httpRequest.HttpResponse
zw resp
do resp.Data.OutputToDevice()

Compare output of

Set sc = httpRequest.Post("/sample/", 1)

with what Postman sends.

Also, what does

Set sc = httpRequest.Post("/sample/")
zw sc

show?

Probably. What setting do you need to modify?

Continuous Delivery - what tools do you use to automate building, testing and deploying your applications?  Do you integrate issue tools/messaging/planning and CD tools?

The easiest solution would be

set net.SSLCheckServerIdentity=0

that disables server cert checking. Not very secure obviously.

What's the use case by the way?

Do you want to change ROWSPEC depending on passed argument?

ROWSPEC can be changed on compilation only and it's rather static. At least xDBC clients depend on declared schema/query info and so it cannot be changed dynamically.

Please post code to reproduce the issue?

Yes, it would work.