fix: add oci as supported container runtime

The oci-systemd-hook sets container=oci for PID 1 when running
systemd inside OCI containers. This value was not recognized by
the container resolver, causing a warning and falling back to
container_other.

Add oci to the list of known container runtimes to resolve the
warning and report the correct virtual fact.

Discovered during e2e tests in openvox-operator.

Author: slauger

lib/facter/resolvers/linux/containers.rb

@@ -52,6 +52,8 @@ def read_environ(fact_name)
               vm = 'podman'
             when 'crio'
               vm = 'crio'
+            when 'oci'
+              vm = 'oci'
             when 'zone'
               return nil
             when 'systemd-nspawn'

spec/facter/resolvers/linux/containers_spec.rb

@@ -92,6 +92,20 @@
     end
   end
 
+  context 'when hypervisor is oci and it is discovered by environ' do
+    let(:cgroup_output) { load_fixture('cgroup_file').read }
+    let(:environ_output) { ['container=oci'] }
+    let(:result) { { oci: {} } }
+
+    it 'return oci for vm' do
+      expect(containers_resolver.resolve(:vm)).to eq('oci')
+    end
+
+    it 'return oci info for hypervisor' do
+      expect(containers_resolver.resolve(:hypervisor)).to eq(result)
+    end
+  end
+
   context 'when hypervisor is illumos' do
     let(:cgroup_output) { nil }
     let(:environ_output) { ['container=zone'] }