Create Named Credentials in Salesforce via Apex

CreateNamedCredsController.cls

public with sharing class CreateNamedCredsController {
  public static final String CLIENT_ID = '<clientid>';
  public static final String CLIENT_SECRET = '<clientsecret>';
  public static final String API_VERSION='v51.0';
  public static final String TOKEN_ENDPOINT_URL = 'https://login.salesforce.com/services/oauth2/token';
  public static final String AUTHORIZE_ENDPOINT_URL = 'https://login.salesforce.com/services/oauth2/authorize';
  public static final String REDIRECT_URL = URL.getSalesforceBaseUrl().toExternalForm()+'/apex/AuthHandler';
  public static final String NAMEDCRED_TOOLING_ENDPOINT_URL = URL.getSalesforceBaseUrl().toExternalForm()+'/services/data/'+API_VERSION+'/tooling/sobjects/NamedCredential/';
  public static final String AUTH_PROVIDER_NAME = 'SF_Auth';
  
  
  public String namedCredName { get; set; }

  public String getAuthUrl() {
    return AUTHORIZE_ENDPOINT_URL+'?response_type=code&client_id='+CLIENT_ID+'&redirect_uri='+REDIRECT_URI+'&scope=api refresh_token&prompt=select_account&state=' +
      this.namedCredName;
  }

  public Pagereference checkAndAct() {
    if (String.isBlank(this.namedCredName) && String.isBlank(Apexpages.currentPage().getParameters().get('state'))) {
      return null;
    }
    if (Apexpages.currentPage().getParameters().containsKey('code')) {
      return this.getTokenAndCreateNamedCred();
    }
    return new Pagereference(this.getAuthUrl());
  }

  public Pagereference getTokenAndCreateNamedCred() {
    String code = Apexpages.currentPage().getParameters().get('code');
    this.namedCredName = Apexpages.currentPage().getParameters().get('state');
    HttpRequest req = new HttpRequest();
    req.setEndpoint(TOKEN_ENDPOINT_URL);
    req.setMethod('POST');
    req.setHeader('Content-Type', 'application/x-www-form-urlencoded');
    String reqBody = '';
    reqBody += 'client_id=' + CLIENT_ID + '&';
    reqBody += 'client_secret=' + CLIENT_SECRET + '&';
    reqBody += 'grant_type=authorization_code&';
    reqBody += 'code=' + code + '&';
    reqBody += 'redirect_uri=' + REDIRECT_URL + '&';
    reqBody += 'format=json';
    req.setBody(reqBody);
    req.setHeader('Content-Length', String.valueOf(reqBody.length()));
    HttpResponse resp = new Http().send(req);
    TokenResponse tok = (TokenResponse) JSON.deserialize(resp.getBody(), TokenResponse.class);
    this.createNamedCred(tok);
    Pagereference ref = Page.AuthHandler;
    ref.setRedirect(true);
    return ref;
  }

  private void createNamedCred(TokenResponse resp) {
    HttpRequest req = new HttpRequest();
    req.setEndpoint(NAMEDCRED_TOOLING_ENDPOINT_URL);
    req.setMethod('POST');
    req.setHeader('Authorization', 'Bearer ' + UserInfo.getSessionId());
    req.setHeader('Content-Type', 'application/json');
    req.setHeader('Content-Type', 'application/json');
    NamedCredMetadata namedCredMdt = new NamedCredMetadata();
    namedCredMdt.authTokenEndpointUrl = TOKEN_ENDPOINT_URL;
    namedCredMdt.label = this.namedCredName;
    namedCredMdt.oauthToken = resp.access_token;
    namedCredMdt.oauthRefreshToken = resp.refresh_token;
    namedCredMdt.endpoint = resp.instance_url + '/services/data/'+API_VERSION;
    namedCredMdt.authProvider = AUTH_PROVIDER_NAME;
    NamedCred namedCred = new NamedCred();
    namedCred.FullName = this.namedCredName.replace(' ', '_');
    namedCred.Metadata = namedCredMdt;
    req.setBody(JSON.serialize(namedCred));
    HttpResponse namedCredResp = new Http().send(req);
    System.debug('>>Response ' + namedCredResp.getbody());
  }

  class NamedCred {
    public NamedCredMetadata Metadata;
    public String FullName;
  }

  class NamedCredMetadata {
    public String authTokenEndpointUrl;
    public String authProvider;
    public String endpoint;
    public String label;
    public String oauthToken;
    public String oauthRefreshToken;
    public String principalType = 'NamedUser';
    public String protocol = 'Oauth';
  }

  class TokenResponse {
    public String refresh_token;
    public String instance_url;
    public String access_token;
  }
}