Lumen as OAuth2 server: how to make an authorization dialog?
Lumen is made for APIs. Many APIs today use OAuth2 mechanism, and the most popular grant is "Authorization code grant" when user is redirected to a web page and asked for permission confirmation like this:
At the same time, Lumen 5.2 lost Views module. So how to implement this page in Lumen today?
If you need a frontend with Lumen you should probably be using Vue, Angular, Ember or such like. I believe it is designed to work as a "microservice", you may have the wrong tools for the job.
I work in a microservices environment which is very complicated and beyond your needs but as an example I use an angular front-end which talks with a common Lumen API (referred to as the frontend-backend). This API is full of custom, business-driven endpoints that are specific to the application. The frontend-backed API makes various calls to various other APIs in order to achieve the business-driven objective. For example; I have an endpoint called "connectToTwitter" which calls our User API, Social Media API and our Twitter API wrapper.