[Code Refactoring]: Update of CLI error handling

[LorenzoTettamanti]

Is your feature request related to a problem?

• No

  Problem Description:

  This issue aims to improve the general CLI code quality; everyone can refer to this issue to commit:

  - error handling improvements
  - cli errors output updates
  - cli code cleanup
  

  Solution:

  TODO:

• create an error.rs module

• update the documentation

• avoid .unwrap() pattern

• avoid repeated code