I'm new to SharePoint development and currently trying to figure out the best approach/technologies to implement the following user experience:
- For every authenticated SharePoint user I want to show a new UI element on every page (button/input field)
- When clicking to that UI element, user should see an HTML UI loaded from my remote server.
- That HTML should be displayed on the top of the page content
- Calls to the back-end server should be done on behalf of the current logged user, so it will be possible to filter back-end response based on the user permissions
Which SPFx components do I need to use for that: webparts, extensions or both?
What about the impersonation? Can I create a SharePoint application that will redirect UI calls to my back-end along with a JWT so I could verify them, serve requests back to the UI?
Last, but not least: would it be possible to have everything above in one application for both SharePoint Online and SharePoint 2019 or would it be two separate apps?