Allow for ignoring certificate checks

[ngetchell]

1. Allow for ignoring certificates in Save-GitlabConfiguration

2. Describe Your Environment

Operating System and PowerShell version:

Name                           Value
----                           -----
PSVersion                      6.2.3
PSEdition                      Core
GitCommitId                    6.2.3
OS                             Linux 5.3.0-23-generic #25-Ubuntu SMP Tue Nov 12 09:22:33 UTC 2019
Platform                       Unix
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

3. Expected Behavior

Test-Gitlabapi should work when you provide otherwise correct information.

4.Current Behavior

Test-GitLabAPI
Invoke-WebRequest : The remote certificate is invalid according to the validation procedure.

5. Possible Solution

-SkipCertificateCheck

6. Context

Unable to use the module when pwsh doesn't trust the GitLab server.