that is all pass-thru data for the identity server to pass back to the callback handler. this data is required by the callback code. it looks like an oauth flow.
decoded ReturnUrl:
/connect/authorize/callback?client_id=brekon
&redirect_uri=https%3A%2F%2Flocalhost%3A44382%2Fauthentication%2Flogin-callback
&response_type=code
&scope=openid%20profile%20email%20api1
&code_challenge=gpralpA1djm4DZs4J-i_SG5aw9mQtMiHpWuh1clq7co
&code_challenge_method=S256
&response_mode=form_post
&nonce=637993598524237769.ZmVjOGI2YTQtZjFlYy00MjMyLWI3NzMtNjRkNTEwZWNlN2YyNzZiMzg2ZDQtZjExZi00ZjYyLThjMGEtMjlkMmQ5NDQ1NjU2
&state=CfDJ8OhhiPHXuTJFtAjFNi6MNVOw-nJmIt80t8l7pELKwDeq77OM1trdr_F10Odc0MDjnLLsXyTU_3pd1Z2uXTZDbjZtFbmLNTsdx4m9h2F5hCwNfR6fxkp1cAXvgwCBGa2oTCqPK--WIxkpoJVMxerN8xkLYfzkgHEDukIqAI2y61Ud2I_rFXyYLmum413YkSjoEQAerfLN-ll3oCyzkV3DXbquvSiDc3T26m3ohkTaqiycmqYpZoqx24Ht1wp5iUFxrjphVm2pmLAkmjU4dcyDW7rSZBcY5OQD66APi8Na3eUE2Zjzl8u99OeDkLh8VpNpmd84XHPnxB2ojqGlySOQBIJdFwZf-TFVAcaKy3Wq2mviInlvr1F-y8j1HUz4WO503cfxq8A1Ex_FYrhshOGuQnc
&x-client-SKU=ID_NETSTANDARD2_0
&x-client-ver=6.10.0.0
normally a controller would generate this with:
return Challenge(
new AuthenticationProperties { RedirectUri = redirectUrl },
scheme);