fix: HTTP 415 error in Grant-SubscriptionCreatorRole by removing incorrect JSON escaping (#486)

# Pull Request

## Issue

Issue #, if available:

## Description

`Grant-SubscriptionCreatorRole` fails with HTTP 415 "Unsupported Media
Type" when attempting to grant the SubscriptionCreator role. The JSON
payload passed to `az rest --body` was being corrupted by escaping all
double quotes:

```powershell
# Before (broken)
$roleAssignmentPayloadJson = $roleAssignmentHashTable | ConvertTo-Json -Depth 100 -Compress
$roleAssignmentPayloadJson = $roleAssignmentPayloadJson -replace '"', '\"'  # ← corrupts JSON

# After (fixed)
$roleAssignmentPayloadJson = $roleAssignmentHashTable | ConvertTo-Json -Depth 100
```

Changes:
- Removed the quote escaping line that was corrupting the JSON payload
- Removed unnecessary `-Compress` parameter
- Added proper quoting around `$roleAssignmentPayloadJson` in the
`--body` argument

## License

By submitting this pull request, I confirm that my contribution is made
under the terms of the projects associated license.

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<details>

<summary>Original prompt</summary>

> ## Problem
> 
> The `Grant-SubscriptionCreatorRole` function is failing with an HTTP
415 "Unsupported Media Type" error when attempting to grant the
SubscriptionCreator role to a service principal.
> 
> ### Error Details
> 
> ```
> ERROR: Unsupported Media
Type({"type":"https://tools.ietf.org/html/rfc9110#section-15.5.16","title":"Unsupported
Media
Type","status":415,"traceId":"00-ac2e62d0a7bdc6a56e8393ae2d2b85af-99be01612e28a53a-01"})
> Grant-SubscriptionCreatorRole: The 'SubscriptionCreator' role could
not be granted to the service principal. Please check the error message
above and try again.
> ```
> 
> ### Example Command
> 
> ```powershell
> Grant-SubscriptionCreatorRole -servicePrincipalObjectId
"e5c27947-cc32-4147-91b7-865ad4536ece" -billingAccountID "7690848"
-enrollmentAccountID "350580"
> ```
> 
> ## Root Cause
> 
> In the file `src/ALZ/Public/Grant-SubscriptionCreatorRole.ps1`, around
line 137-138, the JSON payload is being incorrectly escaped:
> 
> ```powershell
> $roleAssignmentPayloadJson = $roleAssignmentHashTable | ConvertTo-Json
-Depth 100 -Compress
> $roleAssignmentPayloadJson = $roleAssignmentPayloadJson -replace '"',
'\"'
> ```
> 
> The second line escapes all double quotes in the JSON string, which
corrupts the JSON structure. When this malformed string is passed to `az
rest --body`, the Azure REST API rejects it with an HTTP 415 error
because it's no longer valid JSON.
> 
> ## Solution
> 
> Remove the line that escapes the quotes (line 138). The `az rest
--body` parameter can handle the JSON string directly from
`ConvertTo-Json` without additional escaping.
> 
> ### Changes Needed
> 
> In `src/ALZ/Public/Grant-SubscriptionCreatorRole.ps1`:
> 
> 1. Remove the line: `$roleAssignmentPayloadJson =
$roleAssignmentPayloadJson -replace '"', '\"'`
> 2. Optionally remove the `-Compress` parameter from `ConvertTo-Json`
as it's not necessary for `az rest`
> 
> The corrected code should look like:
> 
> ```powershell
> $roleAssignmentPayloadJson = $roleAssignmentHashTable | ConvertTo-Json
-Depth 100
> 
> $grantRbac = $(az rest --method PUT --url
"$managementApiPrefix$($billingResourceID)/billingRoleAssignments/$($roleAssignmentName)?api-version=2024-04-01"
--body "$roleAssignmentPayloadJson") | ConvertFrom-Json
> ```
> 
> ## Testing
> 
> After the fix, the command should successfully grant the
SubscriptionCreator role without the HTTP 415 error.
> 
> ## Files to Modify
> 
> - `src/ALZ/Public/Grant-SubscriptionCreatorRole.ps1` - Remove the
problematic quote escaping line


</details>

*This pull request was created as a result of the following prompt from
Copilot chat.*
> ## Problem
> 
> The `Grant-SubscriptionCreatorRole` function is failing with an HTTP
415 "Unsupported Media Type" error when attempting to grant the
SubscriptionCreator role to a service principal.
> 
> ### Error Details
> 
> ```
> ERROR: Unsupported Media
Type({"type":"https://tools.ietf.org/html/rfc9110#section-15.5.16","title":"Unsupported
Media
Type","status":415,"traceId":"00-ac2e62d0a7bdc6a56e8393ae2d2b85af-99be01612e28a53a-01"})
> Grant-SubscriptionCreatorRole: The 'SubscriptionCreator' role could
not be granted to the service principal. Please check the error message
above and try again.
> ```
> 
> ### Example Command
> 
> ```powershell
> Grant-SubscriptionCreatorRole -servicePrincipalObjectId
"e5c27947-cc32-4147-91b7-865ad4536ece" -billingAccountID "7690848"
-enrollmentAccountID "350580"
> ```
> 
> ## Root Cause
> 
> In the file `src/ALZ/Public/Grant-SubscriptionCreatorRole.ps1`, around
line 137-138, the JSON payload is being incorrectly escaped:
> 
> ```powershell
> $roleAssignmentPayloadJson = $roleAssignmentHashTable | ConvertTo-Json
-Depth 100 -Compress
> $roleAssignmentPayloadJson = $roleAssignmentPayloadJson -replace '"',
'\"'
> ```
> 
> The second line escapes all double quotes in the JSON string, which
corrupts the JSON structure. When this malformed string is passed to `az
rest --body`, the Azure REST API rejects it with an HTTP 415 error
because it's no longer valid JSON.
> 
> ## Solution
> 
> Remove the line that escapes the quotes (line 138). The `az rest
--body` parameter can handle the JSON string directly from
`ConvertTo-Json` without additional escaping.
> 
> ### Changes Needed
> 
> In `src/ALZ/Public/Grant-SubscriptionCreatorRole.ps1`:
> 
> 1. Remove the line: `$roleAssignmentPayloadJson =
$roleAssignmentPayloadJson -replace '"', '\"'`
> 2. Optionally remove the `-Compress` parameter from `ConvertTo-Json`
as it's not necessary for `az rest`
> 
> The corrected code should look like:
> 
> ```powershell
> $roleAssignmentPayloadJson = $roleAssignmentHashTable | ConvertTo-Json
-Depth 100
> 
> $grantRbac = $(az rest --method PUT --url
"$managementApiPrefix$($billingResourceID)/billingRoleAssignments/$($roleAssignmentName)?api-version=2024-04-01"
--body "$roleAssignmentPayloadJson") | ConvertFrom-Json
> ```
> 
> ## Testing
> 
> After the fix, the command should successfully grant the
SubscriptionCreator role without the HTTP 415 error.
> 
> ## Files to Modify
> 
> - `src/ALZ/Public/Grant-SubscriptionCreatorRole.ps1` - Remove the
problematic quote escaping line

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Author: Copilot

src/ALZ/Public/Grant-SubscriptionCreatorRole.ps1

@@ -132,10 +132,9 @@ Grant-SubscriptionCreatorRole -servicePrincipalObjectId "bd42568a-7dd8-489b-bbbb
             "principalTenantId" = $tenantId
         }
     }
-    $roleAssignmentPayloadJson = $roleAssignmentHashTable | ConvertTo-Json -Depth 100 -Compress
-    $roleAssignmentPayloadJson = $roleAssignmentPayloadJson -replace '"', '\"'
+    $roleAssignmentPayloadJson = $roleAssignmentHashTable | ConvertTo-Json -Depth 100
 
-    $grantRbac = $(az rest --method PUT --url "$managementApiPrefix$($billingResourceID)/billingRoleAssignments/$($roleAssignmentName)?api-version=2024-04-01" --body $roleAssignmentPayloadJson) | ConvertFrom-Json
+    $grantRbac = $(az rest --method PUT --url "$managementApiPrefix$($billingResourceID)/billingRoleAssignments/$($roleAssignmentName)?api-version=2024-04-01" --body "$roleAssignmentPayloadJson") | ConvertFrom-Json
 
     if ($null -eq $grantRbac) {
         $errorMessage = "The 'SubscriptionCreator' role could not be granted to the service principal. Please check the error message above and try again."