Need to create a groovy script which triggers notifications on MS Teams when Jira issue createed

[nitsajwa]

When I am trying to POST a REST call via the Postman app , it asks for access token by sending the response like this

{
"error": {
"code": "InvalidAuthenticationToken",
"message": "Access token is empty.",
"innerError":

{ "request-id": "a5c0c665-c446-4c2a-8377-f3c3500829d1", "date": "2019-05-07T10:28:00" }

}
} 
Question 1) From where shall I generate access token key or Bearer token?

Question 2) 
My REST call - https://graph.microsoft.com/beta/teams/Test:2520channel/channels/19:3a3c8d6c46bf3d4437b6377b4389cc8213@thread.skype/messages

where team id -Test:2520channel
and channel id -19:3a3c8d6c46bf3d4437b6377b4389cc8213@thread.skype

and I got these ids from this URL -https://teams.microsoft.com/l/channel/19%3a3c8d6c46bf3d4437b6377b4389cc8213%40thread.skype/Test%2520channel?
groupId=2dc2207c-de56-4b67-a1dd-ad090676f6c5&tenantId=d52c9ea1-7c21-47b1-82a3-33a74b1f74b8
Is it the correct way to fetch team ID and channel id?