ShadowJar minimization

[Sloox]

Investigate the option of turning the minimisation of the shadowjar gradle task to ON.
Also check the consequences as removing classes form the build could lead to errors due to class not found issues.

Additional context
More information here:https://imperceptiblethoughts.com/shadow/configuration/minimizing/
Apart of the #774 issue chain

[Sloox]

After applying the minimization of the ShadowJar which is an inherint inbuild feature there is a reduction of approximately 30%
Total size shrinks from 38.5 to ~ 26.6 MB
The largest reduction of clases comes from the shrinking of unused google classes.
The greatest shrinkages are listed as follows

• com.google : 31.8 -> 16.6 MB
  • common: 10.4 -> 6 MB
  • api: 9.3 -> 3.5 MB
  • protobuf: 6.2 -> 4.2 MB
  • cloud: 2.4 -> 1.6 MB
• com.fasterxml : 7.3 -> 7 MB
• com.ctc.wstx : 5.5 -> 0.2 MB
• io.netty : 12.9 -> 8.4 MB
• io.ktor : 10.9 -> 6.9 MB
• kotlin : 18.5 -> 17.2 MB
• org.apache : 7.7 -> 1.3 MB

When it comes to shrinkages the biggest issue is the removal of classes that are actually needed. the shadowjar minimzation function has limited support for excluding packages when compared to Progaurd/R8.
A thorough test will be needed with a fully built jar as the ./gradlew check command will test it on a non minimized jar.

based on the commit : 83d3606 which is master as of 28/08/2020

[Sloox]

Reopenining due to #1077
& the requirement: #1076 & #1072