How to enable extrernal access to D365 Business Central without asking the users to register using external web portal

For my recent project https://bcrfq.com which is a Request For Quotation app made for Business Central that allows vendors to send their quotes to BC I needed a way to allow the vendors to do it without asking them to sign up to anything. I just wanted to share a link to them and be done with it. Basically its a web app and the user will get a unique url pointing to the document that is assigned to them.