Validate Set-ConfluenceConfig input at the boundary

Reject the reserved 'ID' config key and require PerPage to be a positive integer before persisting, so a caller cannot corrupt the stored configuration or feed an invalid v2 'limit' value into Invoke-ConfluenceRestMethod (review thread on Set-ConfluenceConfig L37).

Author: MariusStorhaug

src/functions/public/Config/Set-ConfluenceConfig.ps1

@@ -31,6 +31,21 @@ function Set-ConfluenceConfig {
     )
 
     Initialize-ConfluenceConfig
+
+    # Guard the boundary before persisting so a caller cannot corrupt the stored configuration:
+    # 'ID' is the reserved context key that identifies the config record itself, and 'PerPage'
+    # is used verbatim as the v2 'limit' query value, so it must be a positive integer.
+    if ($Name -eq 'ID') {
+        throw "The configuration key 'ID' is reserved for internal use and cannot be set."
+    }
+    if ($Name -eq 'PerPage') {
+        $perPage = 0
+        if (-not [int]::TryParse([string]$Value, [ref]$perPage) -or $perPage -lt 1) {
+            throw "PerPage must be a positive integer; received '$Value'."
+        }
+        $Value = $perPage
+    }
+
     if ($PSCmdlet.ShouldProcess("Confluence config '$Name'", 'Set')) {
         $script:Confluence.Config[$Name] = $Value
         $null = Set-Context -ID $script:Confluence.DefaultConfig.ID -Context $script:Confluence.Config -Vault $script:Confluence.ContextVault