Make redirectUrl nullable in providers

[egorksv]

Our case: we have a multitenantend app which can be accessed on different domains.

Each time we authenticate a user, redirectUrl is calculated based on a tenant ID and their registered domain, which causes typing error.

Our current workaround:

declare module 'arctic' {
  export class KeyCloak {
    constructor(realmURL: string, clientId: string, clientSecret: string | null, redirectURI: string | null);
  }
}

This works fine, but would be nice if arctic supported this out of the box

PS: Also realised this is a bit more involved, at this point we're using pnpm patch to sneak in validateAuthorizationCodeWithRedirectUri function to oauth client and keycloak provider, would you be interested in pull request?

[pilcrowonpaper]

Is this issue specifically for Keycloak?