Duplicate redirect_uri in Callback phase

[dombarnes]

Currently using Omniauth-oauth2 v1.8.0 (can't upgrade to 2.0 for IdentityServer reasons) and I've got this in my strategy:

args %i[client_id client_secret client_scope]

      option :name, 'my_provider'
      option :client_options, {
        site: ENV.fetch('OAUTH_SERVER'),
        authorize_url: '/connect/authorize',
        redirect_uri: "#{ENV['APPLICATION_HOST']}/auth/my_provider/callback",
        token_url: '/connect/token'
      }

When I have Debugging on, I see that the redirect_uri param is sent twice, resulinting in invalid grant errors from our Oauth server.

20:37:18 web-ssl.1     | I, [2022-08-29T20:37:18.347420 #7842]  INFO -- request: {"client_id"=>"my_client_id",
20:37:18 web-ssl.1     |  "client_secret"=>"SECRET",
20:37:18 web-ssl.1     |  "grant_type"=>"authorization_code",
20:37:18 web-ssl.1     |  "code"=>"ABC123,
20:37:18 web-ssl.1     |  "redirect_uri"=>"https://myapp.lvh.me:3000/auth/my_provider/callback",
20:37:18 web-ssl.1     |  :redirect_uri=>"https://myapp.lvh.me:3000/auth/my_provider/callback"}

And IdentityServer warns me:

Invalid redirect_uri{ redirectUri = https://myapp.lvh.me:3000/auth/my_provider/callback,https://myapp.lvh.me:3000/auth/my_provider/callback, expectedRedirectUri = https://myapp.lvh.me:3000/auth/my_provider/callback },
 "redirect_uri": "https://myapp.lvh.me:3000/auth/my_provider/callback,https://myapp.lvh.me:3000/auth/my_provider/callback"

If I take out the client_option, I get another separate issue where the callback URL is appending ?return_url=%2F which causes a different issue.