Unimplemented default error handling

[albodelu]

Default error handling was not implemented and I was waiting for your solution.

This is a possible way to manage it. Feel free to close it but I would appreciate your opinion.

I'm not sure if I am breaking SOLID principles but show loading and error message tasks
are very related, and are repetitive tasks that I prefer to move to the base classes.

Now you can pass lambdas to the base disposable observer and add default error handling.

My app uses nullable views so I improvised a solution with lateinit a little strange for me.

Edit: I found this related article for Java:
RxJava2 and Retrofit2 Error Handling on a single place

[android10]

Thanks for the feedback @albodelu. I will close the ticket for now and will take that into consideration.