Webhook 'push event' 'user' data content is not organized consistently with other webhooks
<!--IssueSummary start-->
<details>
<summary>
Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards.
</summary>
- [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=351513)
</details>
<!--IssueSummary end-->
# Rationale
The format for "user" data sent into 'push' and 'tags' webhooks is not consistent with merge request, notes events, issue.
It would be nice & clean to get this uniformized, that would help webhooks recipient code to handle webhooks more cleanly.
# Details
Push events sends multiple ```user_*``` fields:
```python
"user_id": 4,
"user_name": "John Smith",
"user_username": "jsmith",
"user_email": "john@example.com",
```
whereas other webhooks provide an inner structure for 'user'; for instance, issue events :
```python
"user": {
"id": 1,
"name": "Administrator",
"username": "root",
"avatar_url": "http://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=40\u0026d=identicon",
"email": "admin@example.com"
},
```
Not a real blocker point, but I think there's some legacy behind this that could be improved.
# Triage
This can be added to the gitlab-org&2318 epic.
issue