Literal "_none" value saved for seelct fields

Attaching screenshot for reference.

Feedback posted on the MR.

I cranked up my email account linked to drupal.org and saw this thread...

I can't remember the sequence of the field widget submission processing, but can someone manually check that the validation in a required textfield component still triggers if you enter _blank for that component? If it does, the this minor fix may need a tweak to only target option based components.

Feedback posted on the MR.

@heddn In required textfield components i have tested that when we write _none then validation error is not triggering and _none is getting replaced by "" (empty strings) . When we write _blank then also there is no validation error and the field is having _blank value.

I think this could still add some more edge cases to the tests to address #11.

To address #11, I've added test coverage for using "_none" as value for text fields. And the tests are failing. If you for example enter "_none" for the field "Family" an empty value gets saved for that field. If the name field is required you get the more cryptic error message "This value should not be null.".

I've added a possible fix for the case from #11.

Reviewed the MR. Checked all the changes made.
1. Checked that on submitting more than one empty components for the name field, all the "_none" values are replaced by empty strings.
2. Checked that the validation does not trigger if we give "_blank" or "_none" as input.
3. Checked all the tests written and all of them passed.

Hence moving it to RTBC.