feat: envar-controlled connection settings

[DerekRoberts]

https://github.com/bcgov/nr-silva/blob/main/backend/src/main/resources/application.properties#L31-L33

spring.datasource.hikari.minimumIdle = 1
spring.datasource.hikari.maximumPoolSize = 3

via @mishraomp:

move these to env vars
and really bump these up in production
based on the load
may be to 5 or 8 per pod
and get the final number after tuning and put env specific values
may be 2 or 3 in dev and 5 in TEST and 8 in prod