feat: Added URL fetch error handling to test script (#642)

## Description

Handling cases where the URL is wrong or invalid. Will write a warning
and skip the check instead of throwing an exception

Depends on #613 as we should add the same to its telemetry check


| Pipeline |
| - |

|[![avm.res.key-vault.vault](https://github.com/AlexanderSehr/bicep-registry-modules/actions/workflows/avm.res.key-vault.vault.yml/badge.svg?branch=users%2Falsehr%2FerrorHandling&event=workflow_dispatch)](https://github.com/AlexanderSehr/bicep-registry-modules/actions/workflows/avm.res.key-vault.vault.yml)
|

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Co-authored-by: Erika Gressi <[email protected]>

avm/utilities/pipelines/staticValidation/compliance/module.tests.ps1

@@ -1070,7 +1070,18 @@ Describe 'Module tests' -Tag 'Module' {
           }
           $implementedSchema = $templateFileContentBicep[$implementedSchemaStartIndex..$implementedSchemaEndIndex]
 
-          $expectedSchemaFull = (Invoke-WebRequest -Uri $expectedUdtUrl).Content -split '\n'
+          try {
+            $rawReponse = Invoke-WebRequest -Uri $expectedUdtUrl
+            if (($rawReponse.Headers['Content-Type'] | Out-String) -like "*text/plain*") {
+              $expectedSchemaFull = $rawReponse.Content -split '\n'
+            } else {
+              throw "Failed to fetch schema from [$expectedUdtUrl]. Skipping schema check"
+            }
+          } catch {
+            Write-Warning "Failed to fetch schema from [$expectedUdtUrl]. Skipping schema check"
+            return
+          }
+
           $expectedSchemaStartIndex = $expectedSchemaFull.IndexOf("type $udtName = {")
           $expectedSchemaEndIndex = $expectedSchemaStartIndex + 1
           while ($expectedSchemaFull[$expectedSchemaEndIndex] -notmatch '^\}.*' -and $expectedSchemaEndIndex -lt $expectedSchemaFull.Length) {