consider adding exclusion constraint to enforce non-overlapping relation statuses

[stefanprobst]

Is your feature request related to a problem? Please describe.

once the initial data curation is finished, we should consider adding database-level "exclusion constraints" for relations where we want to ensure non-overlapping relation statuses, like is_member vs is_chair, is_partner_institution vs is_national_coordinating institution.

cf. #559, #540

Describe the solution you'd like

see above

Describe alternatives you've considered

No response

Additional context

No response

[vronk]

in principle makes sense