Impersonate role

[palagdan]

Resolve #295

Backend kbss-cvut/record-manager#98

For internal authorization, I created a copy for each role group with the impersonate role, since we don’t support manually assigning roles through a selector.

For Keycloak, I created a composite role called impersonate-role. When a user assigns this role, it also grants the resource_access role from the realm-management client (impersonation). I made this proxy role to allow impersonation to be assigned through realm access.

realm_access - global roles across the realm
resource_access - roles of concrete client

---

I dont know what is wrong with the tests in User Component. They are passed successfully locally. They should be rewritten because they use a very old TestUtils class. I began to rewrite them in #293.

[blcham]

@palagdan thanx, but still failing, do not forget to rebase

[blcham]

@palagdan Regarding 6cf1d60, could you add information on what caused those changes in the tests?