Switch to use Adaptive Cards for teams messages

[JustSlone]

Currently we just send a very basic message to the user and a link back to the issue or PR.

We would like to quote the section of the message that mentions the user.

Basic teams messages do not have support for blockquote, which makes this exceedingly ugly.

We should update the code to do two things

1. Process the message to pull out just the text surrounding the @mention
2. Don't do the cheap block quoting we do today and let the Flow job build an adaptive card
   a. Note: we might want to build the adaptive card in code because putting together complex JSON objects in flow is painful