Allow client identifier to be provided to login

[josephguillaume]

Currently PodOS uses dynamic registration, which runs into the issues with solid-client-authn-js documented in https://github.com/pod-os/PodOS/issues/8

I have established that with some relatively minor changes to solid-client-authn-js a static client (using a client identifier document) is able to restore its previous session without interfering with a client on the same domain that is using dynamic registration.

• For the netlify version, a client identifier document will need to be added.
• To use PodOS elements as web components (or self host), the user will need to create their own client identifier document that lists the required redirect_uris.
• To use PodOS as the databrowser on a pod, additional changes would also be needed if the intention is for a single redirect uri to be used for all resources.

As a first step, PodOS needs to allow clientId to be specified at least in: 1) login in core https://github.com/pod-os/PodOS/blob/19b8fab8cd0167e5a53b0b971ea228accf1b65a8/core/src/authentication/index.ts#L37-L41 2) The corresponding call in pos-login https://github.com/pod-os/PodOS/blob/19b8fab8cd0167e5a53b0b971ea228accf1b65a8/elements/src/components/pos-login/pos-login.tsx#L26

In order for the user to be able to provide their client identifier document to the login component, it appears it would make sense to add a clientId prop to pos-login. To include the clientId in the netlify version, it may also need to be a prop in pos-app-browser and in the Makefile. https://github.com/pod-os/PodOS/blob/19b8fab8cd0167e5a53b0b971ea228accf1b65a8/apps/Makefile#L2

[josephguillaume]

New plan is that pos-app takes the attributes redirectUrl and clientId, and sets them as properties on os.session. os.session.login is changed to use these values. Code will also need handling of missing attributes, and decisions about names for localStorage items:

  async function login(oidcIssuer) {
    localStorage.setItem(this.clientId, oidcIssuer);
    localStorage.setItem(KEY_CURRENT_URL, window.location.href);
    return this.session.login({
      oidcIssuer,
      redirectUrl: this.redirectUrl,
      clientId: this.clientId
    });
  }
  async function logout() {
    localStorage.removeItem(this.clientId);
    return this.session.logout();
  }

No change is needed to the login component.