Field for role mapping is too short

Problem/Motivation

Located in admin/config/people/openid-connect/settings, the experimental feature "EXPERIMENTAL - User role mapping" allow to map Oauth groups with drupal roles.
Unfortunately, the field used is a short unformatted field and it seems it is limited to 128 (maybe) chars.
Users that want to add more than one Oauth value there can see at some point it is impossible to add all the wanted values in one of the field

Steps to reproduce

Add more chars than the ones set in any of the fields there

Proposed resolution

Maybe change to a long-text, un-formatted field

Remaining tasks

User interface changes

Yes, in the UI and rendering the text in the field from existing values

API changes

Data model changes