Really old thread, and I'm brand new to GroupMe bot development. I am a "seasoned" web developer, though. It was super easy to create my first bot, join it to a group, and get the callback_url service working. I also was able to easily have my bot post in the group.
However, I'm having several issues that seem like bugs, although with humility I try to assume I'm just doing something wrong. :)
I can't set the "avatar_url" on my bot. I've tried using the bot creation form and the API--the request returns successfully, but the "avatar_url" is always null.
Worse is that when you click the default avatar on one of the bot's posts in the group, you get some random and apparently real person's profile! It's a different person each time I create a bot.
I've got more issues, but I'll start with those.