Add secret provider functionality and enhance configuration data resolution

Private/Resolve-ConfigurationDataSecretReference.ps1

@@ -0,0 +1,35 @@
+function Resolve-ConfigurationDataSecretReference {
+    [CmdletBinding()]
+    Param(
+        [Parameter(Mandatory=$true)]
+        [System.Collections.IDictionary]
+        $Reference,
+
+        [Parameter(Mandatory=$true)]
+        [ValidateSet("credential", "securestring", "string")]
+        [string]
+        $ExpectedType,
+
+        [Parameter(Mandatory=$false)]
+        [hashtable]
+        $ProviderSettings = @{}
+    )
+
+    $Provider = [string](Get-ConfigurationDataMapValue -Map $Reference -Key "Provider")
+    $ProviderDefinition = Get-ConfigurationDataSecretProvider -Name $Provider
+
+    if($null -eq $ProviderDefinition){
+        throw "Unsupported secret provider [$Provider]."
+    }
+
+    if($ProviderDefinition.SupportedTypes -notcontains $ExpectedType.ToLowerInvariant()){
+        throw "Secret provider [$($ProviderDefinition.Name)] does not support type [$ExpectedType]."
+    }
+
+    $CurrentProviderSettings = @{}
+    if($ProviderSettings.ContainsKey($ProviderDefinition.Name)){
+        $CurrentProviderSettings = $ProviderSettings[$ProviderDefinition.Name]
+    }
+
+    return & $ProviderDefinition.Resolver -Reference $Reference -ExpectedType $ExpectedType -ProviderSettings $CurrentProviderSettings
+}