add sysinfo support (#1500)

For testing certain scenarios with vagrant-libvirt, need in the guest system a
value for the systems serial number in the DMI/SMBIOS system information.
The domain https://libvirt.org/formatdomain.html#smbios-system-information
format of libvirt allows to specify those values.

While adding `-smbios type=1,serial=$serial_value` to the `qemuargs` parameter
of the libvirt provider is already able to achieve this, a dedicated provider config
value adds native support from the `Vagrantfile` layering system. For example,
in the .box included Vagrantfile a random serial number can be enforced by
adding the following:

require 'securerandom'
Vagrant.configure("2") do |config|
  config.vm.provider :libvirt do |libvirt|
    libvirt.dmi_system_serial = SecureRandom.alphanumeric(8).upcase
  end
end

Then in an instance specific Vagrantfile this value can be overwritten by adding:

Vagrant.configure("2") do |config|
  config.vm.provider :libvirt do |libvirt|
    libvirt.dmi_system_serial = "ABCDEFGH"
  end
end

Co-authored-by: Nils Ballmann <nils.ballmann.ext@siemens.com>
Co-authored-by: Darragh Bailey <daragh.bailey@gmail.com>

spec/unit/action/create_domain_spec.rb

@@ -170,6 +170,70 @@ describe VagrantPlugins::ProviderLibvirt::Action::CreateDomain do
           expect(subject.call(env)).to be_nil
         end
       end
+
+      context 'sysinfo' do
+        let(:domain_xml_file) { 'sysinfo.xml' }
+        let(:vagrantfile_providerconfig) do
+          <<-EOF
+          libvirt.sysinfo = {
+            'bios': {
+              'vendor': 'Test Vendor',
+              'version': '',
+            },
+            'system': {
+              'manufacturer': 'Test Manufacturer',
+              'version': '0.1.0',
+              'serial': '',
+            },
+            'base board': {
+              'manufacturer': 'Test Manufacturer',
+              'version': '',
+            },
+            'chassis': {
+              'manufacturer': 'Test Manufacturer',
+              'serial': 'AABBCCDDEE',
+              'asset': '',
+            },
+            'oem strings': [
+              'app1: string1',
+              'app1: string2',
+              'app2: string1',
+              'app2: string2',
+              '',
+              '',
+            ],
+          }
+          EOF
+        end
+
+        it 'should populate sysinfo as expected' do
+          expect(servers).to receive(:create).with(xml: domain_xml).and_return(machine)
+
+          expect(subject.call(env)).to be_nil
+        end
+
+        context 'with block of empty entries' do
+          let(:domain_xml_file) { 'sysinfo_only_required.xml' }
+          let(:vagrantfile_providerconfig) do
+            <<-EOF
+            libvirt.sysinfo = {
+              'bios': {
+                'vendor': 'Test Vendor',
+              },
+              'system': {
+                'serial': '',
+              },
+            }
+            EOF
+          end
+
+          it 'should skip outputting the surrounding tags' do
+            expect(servers).to receive(:create).with(xml: domain_xml).and_return(machine)
+
+            expect(subject.call(env)).to be_nil
+          end
+        end
+      end
     end
 
     context 'connection => qemu:///session' do