Escape non-ascii characters in json payloads.

Even if the content type indicates a valid unicode charset, Zendesk does like non-ascii characters that aren't escaped.

PS 6.2 added the `-EscapeHanding` parameter to `ConvertTo-Json` which can be used.

functions/Invoke-Method.ps1

@@ -164,7 +164,11 @@ function Invoke-Method {
 
     if ($PSBoundParameters.ContainsKey('Body')) {
         if ($ContentType -eq 'application/json') {
-            $params.Body = $Body | ConvertTo-Json -Compress
+            if ($PSVersionTable.PSVersion -ge '6.2.0') {
+                $params.Body = $Body | ConvertTo-Json -Compress -EscapeHandling EscapeNonAscii
+            } else {
+                $params.Body = $Body | ConvertTo-Json -Compress | ConvertTo-UnicodeEscape
+            }
         } else {
             $params.Body = $Body
         }

internal/ConvertTo-UnicodeEscape.ps1

@@ -0,0 +1,46 @@
+function ConvertTo-UnicodeEscape {
+    <#
+    .SYNOPSIS
+        Escapes non-ascii characters in a given string
+    .DESCRIPTION
+        Escapes non-ascii characters in a given string
+    .EXAMPLE
+        PS C:\> 'A Náme' | ConvertTo-UnicodeEscape
+
+        Escapes the `á` to json compliant `\u00E1`
+    .EXAMPLE
+        PS C:\> $data | ConvertTo-Json -Compress | ConvertTo-UnicodeEscape
+
+        Converts `$data` to json and escapes any non ascii characters
+    #>
+    [CmdletBinding()]
+    Param (
+        # String to escape
+        [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
+        [String]
+        $InputObject
+    )
+
+    $output = ''
+
+    foreach ($char in $InputObject.GetEnumerator()) {
+        $i = [int]$char
+
+        if ($i -lt 128) {
+            Write-Debug -Message "$char ($i) does not need escaping."
+            $output += $char
+        } else {
+            Write-Debug -Message "$char ($i) needs escaping."
+
+            $hex = '{0:X}' -f $i
+            Write-Debug -Message "Character as hex: $hex"
+
+            $escape = '\u' + $hex.PadLeft(4, '0')
+            Write-Debug -Message "Full escape sequence: $escape"
+
+            $output += $escape
+        }
+    }
+
+    $output
+}