Update minimum JDK version to 11 & add support to JDK 21

[oswaldobapvicjr]

During an attempt to add support to JDK 21 LTS, I found the following issues:

• The current Mockito version used (4.11.0) was the latest one that still supports JDK 8, but it's failing to create some required mocks using JDK 21.
• JDK 8 is not supported by Oracle since March 2022.
• JDK 11 is not supported by Oracle since September 2023

So, to continue moving forward, supporting JDK 21 fully, we must drop support to JDK 8.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.01%. Comparing base (a6a04db) to head (e8608b5).

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #160   +/-   ##
=========================================
  Coverage     99.01%   99.01%           
  Complexity      462      462           
=========================================
  Files            71       71           
  Lines           911      911           
  Branches         52       52           
=========================================
  Hits            902      902           
  Misses            9        9           

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