User - Get - Cannot retrieve your own user

[Brend-Smits]

Describe the bug
As a registered user, I cannot use the get-user endpoint to retrieve my own profile information.

To Reproduce
Steps to reproduce the behavior:

1. Make a call to /api/User/{{IDENTITY ID HERE}}
2. See that you get 403 Forbidden instead of your user profile

Expected behavior
You should be able to retrieve your own user profile. Users with the right access should be able to retrieve other users as well (by id).

What needs to be done is:

1. If no identity id is entered, assume the user is requesting their own profile and get identity id by HTTPcontext.
2. If the user is requesting their own profile, it's okay and it should always be allowed.
3. If the identity id is specified and they have permission(they have the required role/scope) to request the specific user, it should be allowed.
4. If the identity id is specified but the user does not have required permission and it's not their own identity id, it should return 401 Unauthorized.