[IX] Support text fields as source when creating an extractor

[aphilop]

Is your feature request related to a problem? Please describe. The information extraction feature currently works with PDF documents as source. We want to expand the sources also to text fields within a template so that information can also be extracted from these text fields.

Describe the solution you'd like The dialogue of creating a new extractor should be expanded to display available text fields as sources for the information extraction. An extractor can have as source either PDF documents or text fields.

@juanmnl will add the discussed designs and description of the flow for this enhancement.

[juanmnl]

We are just adding new common sources to the "create extractor" modal, if available. This sources are now selectable through a radio selector as only one source is selectable at once.

Designs

[RafaPolit]

Things to keep in mind while developing this:

• Please, rename "Common sources" to "Source", common sources is what it is listed underneath, and we could find a way to convey why these options are there (Listing options common to selected templates, or something like that), but the user is not selecting "common sources", the user is defining the single source from where to extract data.