Integration tests and examples should be able to compile using a (self-signed) certificate

[johlju]

To be able to make the examples and integration tests secure by default, we need a certificate on the build worker to be able to compile the configurations. Preferably this should be a self-signed certificate that is created for each test run.

This should make sure to take issue #198 in account.
This would close PowerShell/DscResources#87 and help with PowerShell/DscResources#89 as well.

[johlju]

@PlagueHO have written down steps in PowerShell/DscResources#89 (comment) that might be able to be reused, which seems to be the same as in https://docs.microsoft.com/en-us/powershell/dsc/securemof.

[johlju]

The helper function New-DscSelfSignedCertificate would preferably use the PSPKI module on the PowerShell Gallery (https://github.com/Crypt32/PSPKI), but there is a bug using that, see issue PKISolutions/PSPKI#42. Also when running in the build worker it generates this error.

New-SelfSignedCertificateEx : Uninitialized object (Exception from HRESULT: 0x80040007 (OLE_E_BLANK))
At C:\projects\xpsdesiredstateconfiguration\DscResource.Tests\TestHelper.psm1:1812 char:28
+ ... rtificate = New-SelfSignedCertificateEx @newSelfSignedCertificateExPa ...
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : OperationStopped: (:) [New-SelfSignedCertificateEx], COMException
    + FullyQualifiedErrorId : System.Runtime.InteropServices.COMException,New-SelfSignedCertificateEx

https://ci.appveyor.com/project/johlju/xpsdesiredstateconfiguration/build/6.0.104.0

Using the script in the Script Gallery works.

[johlju]

PR #241 now uses the module PSPKI thanks to the author helping to explain what I did wrong!