:fix: set hikari configuration pool to fixed size (more performant)

[riccardomodanese]

Brief description of the PR. Fixes Hikari pool configuration to achieve better performances (fixed size). Should we remove the 2 no more used options like SystemSettingKey.DB_POOL_IDLE_TIMEOUT and SystemSettingKey.DB_POOL_SIZE_MIN and their default values?

Related Issue none

Description of the solution adopted Remove

Screenshots none

Any side note on the changes made none

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 16.81%. Comparing base (e2fd1dc) to head (7b7ff9d).

Additional details and impacted files

[](https://app.codecov.io/gh/eclipse/kapua/pull/4067?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=eclipse) ```diff @@ Coverage Diff @@ ## develop #4067 +/- ## ========================================== Coverage 16.81% 16.81% Complexity 22 22 ========================================== Files 2010 2010 Lines 52256 52257 +1 Branches 4401 4401 ========================================== + Hits 8788 8789 +1 Misses 43071 43071 Partials 397 397 ``` | [Files](https://app.codecov.io/gh/eclipse/kapua/pull/4067?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=eclipse) | Coverage Δ | | |---|---|---| | [...java/org/eclipse/kapua/commons/jpa/DataSource.java](https://app.codecov.io/gh/eclipse/kapua/pull/4067?src=pr&el=tree&filepath=commons%2Fsrc%2Fmain%2Fjava%2Forg%2Feclipse%2Fkapua%2Fcommons%2Fjpa%2FDataSource.java&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=eclipse#diff-Y29tbW9ucy9zcmMvbWFpbi9qYXZhL29yZy9lY2xpcHNlL2thcHVhL2NvbW1vbnMvanBhL0RhdGFTb3VyY2UuamF2YQ==) | `94.11% <100.00%> (+0.36%)` | :arrow_up: |