WIP: Use a new table for user contribution stats

What does this MR do?

It defers the user contribution stats to a new table, instead of the events table.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

This will allow down sizing the events table.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

#22623 (moved)

.gitlab/issue_templates/Bug.md

+Please read this!
+
+Before opening a new issue, make sure to search for keywords in the issues
+filtered by the "regression" or "bug" label:
+
+- https://gitlab.com/gitlab-org/gitlab-ce/issues?label_name%5B%5D=regression
+- https://gitlab.com/gitlab-org/gitlab-ce/issues?label_name%5B%5D=bug
+
+and verify the issue you're about to submit isn't a duplicate.
+
+Please remove this notice if you're confident your issue isn't a duplicate.
+
+------
+
 ### Summary
 
 (Summarize the bug encountered concisely)
@@ -6,14 +20,20 @@
 
 (How one can reproduce the issue - this is very important)
 
-### Expected behavior
+### Example Project
 
-(What you should see instead)
+(If possible, please create an example project here on GitLab.com that exhibits the problematic behaviour, and link to it here in the bug report)
+
+(If you are using an older version of GitLab, this will also determine whether the bug has been fixed in a more recent version)
 
-### Actual behavior
+### What is the current *bug* behavior?
 
 (What actually happens)
 
+### What is the expected *correct* behavior?
+
+(What you should see instead)
+
 ### Relevant logs and/or screenshots
 
 (Paste any relevant logs - please use code blocks (```) to format console output,
@@ -21,24 +41,42 @@ logs, and code as it's very hard to read otherwise.)
 
 ### Output of checks
 
-#### Results of GitLab application Check
+(If you are reporting a bug on GitLab.com, write: This bug happens on GitLab.com)
+
+#### Results of GitLab environment info
+
+<details>
+<summary>Expand for output related to GitLab environment info</summary>
+<pre>
 
 (For installations with omnibus-gitlab package run and paste the output of:
-`sudo gitlab-rake gitlab:check SANITIZE=true`)
+`sudo gitlab-rake gitlab:env:info`)
 
 (For installations from source run and paste the output of:
-`sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true`)
+`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)
 
-(we will only investigate if the tests are passing)
+</pre>
+</details>
 
-#### Results of GitLab environment info
+#### Results of GitLab application Check
+
+<details>
+<summary>Expand for output related to the GitLab application check</summary>
+<pre>
 
 (For installations with omnibus-gitlab package run and paste the output of:
-`sudo gitlab-rake gitlab:env:info`)
+`sudo gitlab-rake gitlab:check SANITIZE=true`)
 
 (For installations from source run and paste the output of:
-`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)
+`sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true`)
+
+(we will only investigate if the tests are passing)
+
+</pre>
+</details>
 
 ### Possible fixes
 
 (If you can, link to the line of code that might be responsible for the problem)
+
+/label ~bug