Refactors the period selector component now that the design / system is
pretty much finished.
Main points are: change from using CSS selectors to using styled
components; use props instead of classes. This is in keeping with the
general Unleash approach.
There's two very slight visual changes here:
1. There is 4px of added space below the "range" "header" text.
2. The months in the grid are a little closer together and not as wide.
This is because we remove the explicit column gap due to the grid having
a set width. Previously the width was automatic, but because we want
this to line up with the button, we need to set the width explicitly on
both items. As such, with the padding, the grid was a little too wide,
so there was too little padding on the right. This rectifies that.
This PR refactors the `NetworkTrafficUsage.tsx` and `useTrafficData`
files a bit.
The primary objective was to make the network traffic usage component
easier to work with, so I suggest to the reviewer that they start there.
Part of that refactoring, was taking things out of the useTraffic hook
that didn't need to be there. In the end, I'd removed so much that I
didn't even need the hook itself in the new component, so I switched
that to a regular useState.
It made more sense to me to put some of the functions inside the hook
into a separate file and import them directly (because they don't rely
on any hook state), so I have done that and removed those functions from
the trafficData hook. In this case, I also moved the tests.
I have not added any new tests in this PR, but will do so in a
follow-up. The functions I intend to test have been marked as such.
## About the changes
This gives us the ability to communicate other license messages which
are not errors. By default they'll be warning but I'm opening the
possibility of using a backend-provided value to make them informative
instead of warning.
The intention is to communicate things like:
- Your license is about to expire in x days.
- You are getting close to the maximum number of seats in your license
- etc
Wraps the datepicker in a popover, making it function largely the same
as a dropdown list.
The dropdown displays one of:
- "current month" if you've selected the current month
- "<month> <year>" (e.g. "December 2024") if you've selected a month
that isn't the current month
- "Last n months" (e.g. "Last 3 months") if you have selected a range
Additionally, the range selections have been updated to span the whole
row, aligning with the look of generic dropdown lists.

Like with the rest of this file (`PeriodSelector`), the code is rough
and not according to Unleash standards. However, I'm prioritizing fast
changes so UX can have a look before I clean up the code to switch to
using styled components etc later. It's still behind a flag, so I'm not
very worried about it.
This makes the width of the highlight bars in the network dynamic and
based on the number of labels included in the chart.
Since the number of labels should always correspond to the number of
data points, this seems like a sensible approach.
With this, the label width will now be calculated on the fly, so even if
you resize the window or change the number of labels, the highlighting
will still work as expected.
Daily view:

Monthly aggregate:

The labels are now a little narrower on the daily graphs, but it avoids
them being super wide on the monthly graphs
Adds support for the new /traffic-search API behind a flag. When active, you'll be able to select month ranges as well as specific single months.
Largely copies the existing network traffic component, and adds some minor tweaks to make it work with the new data.
This is quite rough, but it gives us a base to build on for later. There's still things that we need to solve for in following PRs.
This PR sets up the application to accept a value from a variant we
control to set the font size of the application on a global level. If it
fails, the value falls back to the previously set CSS value.
This PR implements a first version of the new month/range picker for the
data usage graphs. It's minimally hooked up to the existing
functionality to not take anything away.
This primary purpose of this PR is to get the design and interaction out
on sandbox so that UX can have a look and we can make adjustments.
As such, there are a few things in the code that we'll want to clean up
before removing the flag later:
- for faster iteration, I've used a lot of CSS nesting and element
selectors. this isn't usually how we do it here, so we'll probably want
to extract into styled components later
- there is a temporary override of the value in the period selector so
that you can select ranges. It won't affect the chart state, but it
affects the selector state. Again, this lets you see how it acts and
works.
- I've added a `NewHeader` component because the existing setup smushed
the selector (it's a MUI grid setup, which isn't very flexible). I don't
know what we want to do with this in the end, but the existing chart
*does* have some problems when you resize your window, at least
(although this is likely due to the chart, and can be solved in the same
way that we did for the personal dashboards).

This PR updates the tooltip date display in the traffic usage chart to
use the user's chosen locale settings, falling back to en-US if the
settings are unavailable or otherwise unset.
So, for instance, if I have set my locale to "ja-JP", I'd get this
instead of the en US format:
