For integrations at the instance level we have custom settings that
can be configured at the group and project levels by project/group
maintainers.

For instance specific integrations (e.g Beyond Identity) this change
introduces a similar concept except the only difference in the custom
setting is whether or not the integration is active such settings are
only configurable by instance admins.

This commit introduces services to create and destroy such settings.
Where destroying in this context is just using the same settings as
the instance integration.

Contributes to: #454372
Changelog: added