SAML Implementation is getting 400s when being routed through `redirect_uri`

Using the recently 1.0 oidc middleware, I have set up a sample node application, however upon logging in I am getting this 400 error

The 'redirect_uri' parameter must be an absolute URI that is whitelisted in the client app settings.

According to what I am reading here, either A) my route http://localhost:8080 should be added to either Trusted Origins or as a “Login redirect URI. I see neither option in my app config. I have that address set as Single Sign On URL, Recipient URL, Destination URL, and Audience Restriction (I believe these must be the defaults as I do not specifically recall a reason for having them set so), however I cannot see a way to provide a Trusted Origin. My EpressOIDC config object:

const oidc = new ExpressOIDC({
  issuer: `${process.env.IDP_ISSUER}/oauth2/default`,
  client_id: process.env.IDP_CLIENT_ID,
  client_secret: process.env.IDP_CLIENT_SECRET,
  redirect_uri: 'http://localhost:8080/callback',
  routes: {
    callback: { defaultRedirect: '/dashboard' }
  scope: 'openid profile'