Help with Rest Notify Setup for GroupMe

Configuration
1

I’m struggling here and would appreciate some insight! The curl command below works just fine to post a message to a group in GroupMe:

curl -X POST 'https://api.groupme.com/v3/groups/<My Group ID>/messages' -H 'Content-Type: application/json' -H 'X-Access-Token: <My Token>' -d '{"message":{"source_guid":"ABCD1234","text":"Hello World!"}}'

Here is my notify config (in configuration.yaml) that I can’t get to work.

notify:
  - name: GroupMe
    platform: rest
    resource: https://api.groupme.com/v3/groups/<My Group ID>/messages
    method: POST
    headers: 
      content-type: application/json
      X-Access-Token: <My token>
    message_param_name: text
    data: 
      message:
        source_guid: ABCD1234

When I call this from Developer Tools - Services in HA (with the message field set to ‘Hello World’) I see in the HA logs:

[homeassistant.components.rest.notify] Client error. Response 400: Bad Request: NoneType: None

I sure wish the doc page here had a few more examples!

Any help appreciated!

2

No help here I guess. Too bad, I hate it when I can’t figure out how to take advantage of documented HA functions!

Anyway, I did find a work-around. THis seems to work:

rest_command:
  post_groupme:
    url: https://api.groupme.com/v3/groups/<My Group>/messages
    method: POST
    headers:
      content-type: application/json
      X-Access-Token: <My Token>
    payload: '{"message":{"source_guid":"ABCD1234", "text":"{{ message }}" }}'