Updates the instance stats endpoint with
- maxEnvironmentStrategies
- maxConstraints
- maxConstraintValues
It adds the following rows to the front end table:
- segments (already in the payload, just not used for the table before)
- API tokens (separate rows for type, + one for total) (also existed
before, but wasn't listed)
- Highest number of strategies used for a single flag in a single
environment
- Highest number of constraints used on a single strategy
- Highest number of values used for a single constraint

Turns out we've been trying to return API token data in instance stats
for a while, but that the serialization has failed. Serializing a JS map
just yields an empty object.
This PR fixes that serialization and also adds API tokens to the
instance stats schema (it wasn't before, but we did return it). Adding
it to the schema is also part of making resource usage visible as part
of the soft limits project.
As part of more telemetry on the usage of Unleash.
This PR adds a new `stat_` prefixed table as well as a trigger on the
events table trigger on each insert to increment a counter per
environment per day.
The trigger will trigger on every insert into the events base, but will
filter and only increment the counter for events that actually have the
environment set. (there are events, like user-created, that does not
relate to a specific environment).
Bit wary on this, but since we truncate down to row per (day,
environment) combo, finding conflict and incrementing shouldn't take too
long here.
@ivarconr was it something like this you were considering?
## About the changes
- `getActiveUsers` is using multiple stores, so it is refactored into
read-model
- Refactored Instance stats service into `features` to co-locate related
code
Closes https://linear.app/unleash/issue/UNL-230/active-users-prometheus
### Important files
`src/lib/features/instance-stats/getActiveUsers.ts`
## Discussion points
`getActiveUsers` is coded less _class-based_ then previous similar
read-models. In one file instead of 3 (read-model interface, fake read
model, sql read model). I find types and functions way more readable,
but I'm ready to refactor it to interfaces and classes if consistency is
more important.