thank you all for your help

It wasn't the complete solution, but you showed me the right direction

I managed to do it now with the following setup:

I used the Operation from Base/Library/Operations/HTTP Client/v2.0/Http Client Post

and then filled out the variables as follows (additional notes are in braces like this sentence):

url = url for getting the oauth token

authType = Basic

username = Client Identification (this username will then be used for the Basic encoding as set by the authType)

password = Client Secret (this password will then be used for the Basic encoding as set by the authType)

preemtiveAuth = true (for testing purposes, to ensure the call goes through)

trustAllRoots = true (again for testing purposes, to ensure the call goes through)

x509HostnameVerifier = allow_all (again for testing purposes, to ensure the call goes through)

headers = (nothing, leave this variable empty)

responseCharacterSet = UTF-8 (this is by default some ISO-8859 and will most likely not work like this, so setting this to UTF-8 is really important!)

body = grant_type=password&username=${ressource-owner-username}&password=${ressource-owner-password}    (here the "Ressource Owner Name" and the "Ressource Owner Password" are used as a variable within the entry for the body)

contentType = application/x-www-form-urlencoded

requestCharacterSet = UTF-8 (again, any other encoding will likely not work)

method = POST

thank you all for your help

It wasn't the complete solution, but you showed me the right direction

I managed to do it now with the following setup:

I used the Operation from Base/Library/Operations/HTTP Client/v2.0/Http Client Post

and then filled out the variables as follows (additional notes are in braces like this sentence):

url = url for getting the oauth token

authType = Basic

username = Client Identification (this username will then be used for the Basic encoding as set by the authType)

password = Client Secret (this password will then be used for the Basic encoding as set by the authType)

preemtiveAuth = true (for testing purposes, to ensure the call goes through)

trustAllRoots = true (again for testing purposes, to ensure the call goes through)

x509HostnameVerifier = allow_all (again for testing purposes, to ensure the call goes through)

headers = (nothing, leave this variable empty)

responseCharacterSet = UTF-8 (this is by default some ISO-8859 and will most likely not work like this, so setting this to UTF-8 is really important!)

body = grant_type=password&username=${ressource-owner-username}&password=${ressource-owner-password}    (here the "Ressource Owner Name" and the "Ressource Owner Password" are used as a variable within the entry for the body)

contentType = application/x-www-form-urlencoded

requestCharacterSet = UTF-8 (again, any other encoding will likely not work)

method = POST