Which the correct way to implement an API request

I’m trying to create a request like that, but with ruby.

curl --request POST \
--url '{BASE_URL}/oauth2/token' \
--header 'Authorization: Basic {BASIC_CLIENT}' \
--header 'Content-Type: application/x-www-form-urlencoded' \
--data grant_type=client_credentials

Im trying like this:

require 'uri'
require 'net/http'

url = URI("https://api.userede.com.br/redelabs/oauth2/token")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = http.post(
  url,
  { 'grant_type' => 'client_credentials' }.to_json,
  { 'Authorization' => "Basic #{CLIENTID}", 'Content-Type' => 'application/x-www-form-urlencoded'}
)

But i’m getting the following error:

{\"error_description\":\"OAuth 2.0 Parameter: grant_type\",\"error\":\"invalid_request\",\"error_uri\":\"https://datatracker.ietf.org/doc/html/rfc6749#section-5.2\"}

>Solution :

You’re formatting the request as JSON, but the system is expecting application/x-www-form-urlencoded.

Replace this:

{ 'grant_type' => 'client_credentials' }.to_json,

with this:

"grant_type=client_credentials",

to conform to the correct payload type.

That may not be the only error, but it is an obvious one.