[WIP] plug gravatar field on api

                            
|Q            |A           |
|---          |---         |
|Bug Fix?     |no          |
|New Feature? |yes         |
|BC Breaks?   |no          |
|Deprecations?|no          |
|Tests Pass?  |yes         |
|Fixed Tickets|#JOINDIN-464|
|License      |MIT         |
|Doc PR       |            |
                            


 Sent using [Gush](https://github.com/gushphp/gush)