Fix labels in events being treated as full label objects (#306)

`Get-GitHubEvent` is currently broken if the issue contains and event that includes the "label" or "labels" property. This is because `Add-GitHubEventAdditionalProperties` treats the labels in the event object as full fledged label objects that normally contain a URL property and other additional pieces of data. The label property in a `GitHub.Event` is a lighter-weight object that simply contains the string for the label and color that was changed, it is not the full object that you would typically receive from a call like `Get-GithubLabel`. 

Updated to add a new `GitHub.LabelSummary` type to describe this scenario, as well as passing in the needed `RepositoryUrl` when adding the additional label properties.

Author: joseartrivera

GitHubEvents.ps1

@@ -3,6 +3,7 @@
 
 @{
     GitHubEventTypeName = 'GitHub.Event'
+    GitHubLabelSummaryTypeName = 'GitHub.LabelSummary'
  }.GetEnumerator() | ForEach-Object {
      Set-Variable -Scope Script -Option ReadOnly -Name $_.Key -Value $_.Value
  }
@@ -237,12 +238,12 @@ filter Add-GitHubEventAdditionalProperties
 
             if ($null -ne $item.label)
             {
-                $null = Add-GitHubLabelAdditionalProperties -InputObject $item.label
+                $null = Add-GitHubLabelAdditionalProperties -InputObject $item.label -TypeName $script:GitHubLabelSummaryTypeName -RepositoryUrl $repositoryUrl
             }
 
             if ($null -ne $item.labels)
             {
-                $null = Add-GitHubLabelAdditionalProperties -InputObject $item.labels
+                $null = Add-GitHubLabelAdditionalProperties -InputObject $item.labels -TypeName $script:GitHubLabelSummaryTypeName -RepositoryUrl $repositoryUrl
             }
 
             if ($null -ne $item.milestone)

GitHubLabels.ps1

@@ -1327,6 +1327,10 @@ filter Add-GitHubLabelAdditionalProperties
     .PARAMETER InputObject
         The GitHub object to add additional properties to.
 
+    .PARAMETER RepositoryUrl
+        Optionally supplied if the Label object doesn't have this value already
+        (as is the case for GitHub.LabelSummary).
+
     .PARAMETER TypeName
         The type that should be assigned to the object.
 
@@ -1346,6 +1350,8 @@ filter Add-GitHubLabelAdditionalProperties
         [AllowEmptyCollection()]
         [PSCustomObject[]] $InputObject,
 
+        [string] $RepositoryUrl,
+
         [ValidateNotNullOrEmpty()]
         [string] $TypeName = $script:GitHubLabelTypeName
     )
@@ -1356,9 +1362,13 @@ filter Add-GitHubLabelAdditionalProperties
 
         if (-not (Get-GitHubConfiguration -Name DisablePipelineSupport))
         {
-            $elements = Split-GitHubUri -Uri $item.url
-            $repositoryUrl = Join-GitHubUri @elements
-            Add-Member -InputObject $item -Name 'RepositoryUrl' -Value $repositoryUrl -MemberType NoteProperty -Force
+            if (-not [System.String]::IsNullOrEmpty($item.url))
+            {
+                $elements = Split-GitHubUri -Uri $item.url
+                $RepositoryUrl = Join-GitHubUri @elements
+            }
+
+            Add-Member -InputObject $item -Name 'RepositoryUrl' -Value $RepositoryUrl -MemberType NoteProperty -Force
 
             if ($null -ne $item.id)
             {