Usage Trends - instance-level VSM
## Problem
We already show some of this information in the admin dashboard (see below), but it's not visualized and shows cumulative info; it's not immediately obvious that the instance is actively being used and users are getting lots of value.
**JTBD:** When my organisation is adopting new workflows, tools & practices; I want to know what tools are adopted and how they are used; so that I can understand progress, determine ROI and report to leadership.
**User story:** As a GitLab champion, I'd like to be able to share an "at-a-glance" view of GitLab adoption with others. I should be able to quickly showcase and understand trends on how GitLab is being used, clearly showing the value of the application.
## Proposal
In the admin dashboard, add a "Usage Trends" page to the Analytics sidebar (https://gitlab.com/gitlab-org/gitlab/-/issues/233833):
* Show the total number of users, projects, groups, issues, MRs, and pipelines on the instance.
* Show a line chart displaying the total number of users on the instance over time, grouped by month. Data accurate up to last day of calendar month.
* Query for this info daily, showing when the data was last updated.
* ~Default time span = 12 months
* We are doing this at the instance-level first because the target user is an admin or engineering director who is interested in the ROI of GitLab as a tool. This information could also be useful to other users of GitLab but is [significantly more complicated](https://gitlab.com/groups/gitlab-org/-/epics/4147#note_415603249) to put at the group level, therefore we are starting with the instance level.

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<summary>Previous image</summary>

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### Open questions
* Can we do this at the group level instead and get the same benefit? Can we avoid admin-level things to maximize the users who benefit and enable this for GitLab.com?
## Examples
* http://gitlab.slack.com/stats
epic