code: function providerExists (uri) {
    let providerOrigin = (new URL(uri)).origin
    let providerConfigUri = providerOrigin + '/.well-known/openid-configuration'
  
    return fetch(providerConfigUri, { method: 'HEAD' })
      .then(result => {
        if (result.ok) {
          return providerOrigin
        }
  
        return null
      })
  }
docs: @param uri {string} Provider URI or Web ID URI
  
  @returns {Promise<string|null>} Returns the Provider URI origin if an OIDC
  provider exists at the given uri, or `null` if none exists