Embedding report in external app with non-Power BI users

mda

1. The registered Azure APP doesn't have anything to do with Power BI reports except to get the accesstoken. If you want to embed your reports in an external application you have to publish it to PowerBI service,

2.You could get the accesstoke and embedded token via two REST APIs as below.

--get the access token
POST /common/oauth2/token HTTP/1.1
Host: login.windows.net
Cache-Control: no-cache 
Content-Type: application/x-www-form-urlencoded

client_id=49dxxxxxxxthe register app client idxxxxx0-6d93f770d1a4&grant_type=password&resource=https%3A%2F%2Fanalysis.windows.net%2Fpowerbi%2Fapi&username=yourpowerbiaccount&password=yourpowerbipassword

--To get the embedded token for a report/dashboard/tile
--reference https://msdn.microsoft.com/en-us/library/mt784614.aspx

POST /v1.0/myorg/groups/dc5811-YOURGROUPID-f16b6c15/reports/16d21d5a-YOURreportID--46a2fd9/GenerateToken HTTP/1.1
Host: api.powerbi.com
Content-Type: application/json
Authorization: Bearer theTokenFromPriorAPI
Cache-Control: no-cache 

{
 "accessLevel": "View"
}

3. Yes, it needs a Premium licence if you want to use  Embedding with non-Power BI users (app owns data). For cost-saving, a more simpler approach would be using Publish to web, you don't have to apply option 1&2.