How to set username and password in IdentityServer4Provider using NextAuth?

I want to authenticate using NextAuth and IdentityServer4. I have created the following provider:

import NextAuth from "next-auth"
import IdentityServer4Provider from "next-auth/providers/identity-server4";

export default NextAuth({
    // Configure one or more authentication providers
    providers: [
      IdentityServer4Provider({
        id: "identity-server4",
        name: "IdentityServer4",
        authorization: { params: { scope: "openid profile email api phone offline_access" } },
        issuer:  "https://localhost:4445/connect/token",
        clientId: "clientId",
        clientSecret: "clientSecret"
      })
    ],
  })

The problem I am having is I need to add a username and password to this setup.

When I look at the code for IdentityServer4 provider in NextAuth, I found this (no username nor password fields):

/** @type {import(".").OAuthProvider} */
export default function IdentityServer4(options) {
  return {
    id: "identity-server4",
    name: "IdentityServer4",
    type: "oauth",
    wellKnown: `${options.issuer}/.well-known/openid-configuration`,
    authorization: { params: { scope: "openid profile email" } },
    checks: ["pkce", "state"],
    idToken: true,
    profile(profile) {
      return {
        id: profile.sub,
        name: profile.name,
        email: profile.email,
        image: null,
      }
    },
    options,
  }
}

How can I add this to the provider?