add password-based login endpoint

Foxchat.Identity/Utils/OauthUtils.cs

@@ -24,11 +24,4 @@ public static class OauthUtils
             return false;
         }
     }
-
-    public static Application GetApplicationOrThrow(this HttpContext context)
-    {
-        var token = context.GetToken();
-        if (token is not { Account: null }) throw new ApiError.Forbidden("This endpoint requires a client token.");
-        return token.Application;
-    }
 }