Add auth support to [Reddit] badges (#10790)

* Add auth support to [Reddit] badges

* Simplify token response schema

doc/production-hosting.md

@@ -24,6 +24,7 @@ Production hosting is managed by the Shields ops team:
 | Cloudflare (CDN)              | Access management           | @espadrine                                                      |
 | Cloudflare (CDN)              | Admin access                | @calebcartwright, @chris48s, @espadrine, @paulmelnikow, @PyvesB |
 | Twitch                        | OAuth app                   | @PyvesB                                                         |
+| Reddit                        | OAuth app                   | @chris48s, @PyvesB                                              |
 | Discord                       | OAuth app                   | @PyvesB                                                         |
 | YouTube                       | Account owner               | @PyvesB                                                         |
 | GitLab                        | Account owner               | @calebcartwright                                                |

doc/server-secrets.md

@@ -290,6 +290,17 @@ Create an account, sign in and obtain generate a key on your
 `PYPI_URL` can be used to optionally send all the PyPI requests to a Self-hosted Pypi registry,
 users can also override this by query parameter `pypiBaseUrl`.
 
+### Reddit
+
+Using a token for Reddit is optional but will allow higher API rates.
+
+- `REDDIT_CLIENT_ID` (yml: `private.reddit_client_id`)
+- `REDDIT_CLIENT_SECRET` (yml: `private.reddit_client_secret`)
+
+Register to use the API using [this form](https://support.reddithelp.com/hc/en-us/requests/new?ticket_form_id=14868593862164)
+and create an app in the [Reddit preferences page](https://www.reddit.com/prefs/apps)
+in order to obtain a client id and a client secret for making Reddit API calls.
+
 ### SymfonyInsight (formerly Sensiolabs)
 
 - `SL_INSIGHT_USER_UUID` (yml: `private.sl_insight_userUuid`)