Add secret provider functionality and enhance configuration data resolution

Private/Get-ConfigurationDataSecretProvider.ps1

@@ -0,0 +1,19 @@
+function Get-ConfigurationDataSecretProvider {
+    [CmdletBinding()]
+    Param(
+        [Parameter(Mandatory=$true)]
+        [string]
+        $Name
+    )
+
+    if($null -eq $script:ConfigurationDataSecretProviders){
+        $script:ConfigurationDataSecretProviders = @{}
+    }
+
+    $ProviderName = $Name.ToLowerInvariant()
+    if(-not $script:ConfigurationDataSecretProviders.ContainsKey($ProviderName)){
+        return $null
+    }
+
+    return $script:ConfigurationDataSecretProviders[$ProviderName]
+}