Use attribute based access control in KeycloakAuthManager

[vincbeck]

While working on implementing is_authorized_dag I realized using ABAC (attribute based access control) would makes more sense and simplify everything. In the previous implementation, for each access control, we were checking:

• Whether the user has access to the entity type
• Whether the user has access to the resource itself

Example. If a user tries to access the variable test, we were checking whether the user has access to all variables, if not, we were checking whether the user has access to the variable test.

Now we are doing only one check: whether the user has access to variables and pass the variable key as an attribute. On Keycloak side then, it is up to the admin to use these attributes in policies. You can see examples of such policies here.

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[bugraoz93]

This is an amazing addition! Thanks, Vincent!

Small update: I have started working on one of the items. I will share as a pull request soon. Most parts done, I need to add some refresh in the auth manager and make the calls.