How to configure a repository and SAIL Configuration with authentication?

Question

I need to create an openrdf:SailRepository in which to authenticate with basic authentication with username and password to a service. I tried the following configuration of the repository, but I don't know how to set the username and password to connect to the service.

PREFIX repo: <http://www.openrdf.org/config/repository#>
PREFIX reposail: <http://www.openrdf.org/config/repository/sail#>
PREFIX ephedra: <http://www.metaphacts.com/ontologies/platform/ephedra#>
PREFIX sail: <http://www.openrdf.org/config/sail#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX : <http://www.metaphacts.com/ontologies/platform/service/custom#>

[] a repo:Repository ;
  repo:repositoryID "rest-api-wrapper" ; 
  rdfs:label "Repository to connect to a remote REST API." ; 
  repo:repositoryImpl [
    repo:repositoryType "openrdf:SailRepository" ;
    reposail:sailImpl [
      sail:sailType "metaphacts:RESTService" ;
      ephedra:serviceURL "http://example.org/rest/service/api" ; 
      ephedra:httpMethod "POST" ; 
      ephedra:httpHeader [
       ephedra:name "Authorization";
       ephedra:value "Basic Auth"
      ] ;
      ephedra:implementsService ephedra:service-name 
    ]  
  ] .

I looked over the documentation on hhttps://rdf4j.org/documentation/reference/configuration/#SailRepository but I don't find any example with the basic authorization concept. Also I need to be able to also configure the body of the POST request. How could I change the template above to add the username, password and the body parameters of the request?