According to this IDEF1X cheat sheet, the diamond shows a relationship of an optional iam_project with zero, one or many iam_project_rules.
The optional can only be on the iam_project side, since iam_project_rules is already "optional" (since there can be zero rules associated with an iam_project).
This is possible since the relation is between ...
This is just static data. Static does not mean it never changes, just that doesn't change often.
Store it in a lookup table in the database, linked by foreign key to whatever the main entity is.
As pointed out in the comments, by @cdkMoose, this is actually no different than the Country data. Countries come and go a surprising amount.
In code, refer to ...
First think about the possibility that these are are two different classes of objects in your domain (as proposed by doubleYou).
But should you really want dynamic objects ('dynamic object' appears to be a good name for the pattern; more informally, i've seen it called 'duck typing' as well) then there are several options available:
There are various ...