Read config variable for restricting access to issues to certain Roles

[acorbi]

Some CKAN instances might want to restrict the access to the Issue information to only certain user roles. Im thinking about scenarios such as:

• Only ADMIN and EDITOR users within an organization plus the creator of the dataset are allowed to access the Issues information
• Only ADMIN users within an organization plus the creator of the dataset are allowed to access the Issues information
• Everyone (even unregistered users) is able to access the Issues information

For this, a new variable could be added to the configuration file (suggestion ckanext.issues.minimun_role_required) which allows to specify the minimum role required for users to access the Issues information both on the Web UI and API. Possible values would be:

• Member
• Editor
• Admin