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.
