Powershell function(s) to Flatten JSON to the expected Key/Value format used by Azure.

Flatten-Json.ps1

Function Flatten-Json() {
    Param(
        [Parameter(Mandatory)]
        [Object]
        $JsonObject,

        [Parameter(Mandatory = $False)]
        [String]
        $Delimiter = ":"
    )

    <#
        .DESCRIPTION
        Powershell function(s) to Flatten JSON to the expected Key/Value format used by Azure.
        
        .PARAMETER JsonObject
        Specifies the converted appsettings.json file.

        .PARAMETER JsonObject
        Specifies the delimiter between nested keys. Default is colon (':').

        .OUTPUTS
        HashTable that contains the flattened json properties and values.
        
        .EXAMPLE
        $json = Get-Content '.\appSettings.json' -Raw | ConvertFrom-Json
        PS> Flatten-Json $json

        .LINK
        https://docs.microsoft.com/en-us/azure/app-service/configure-common
    #>

    $HashTable = @{}
    Flatten-JsonHelper -JsonObject $JsonObject -Delimiter $Delimiter -HashTable $HashTable
    return $HashTable
}
Function Flatten-JsonHelper() {
    Param(
        [Parameter(Mandatory)]
        [Object]
        $JsonObject,

        [Parameter(Mandatory)]
        [String]
        $Delimiter,

        [Parameter(Mandatory)]
        [HashTable]
        $HashTable,

        [Parameter(Mandatory = $False)]
        [AllowEmptyString()]
        [String]
        $Prefix
    )

    if ($JsonObject -eq $null) {
        return
    }
    
    [string] $pre = ''
    foreach ($property in $JsonObject.PSObject.Properties) {
        if ($property.MemberType -ne 'NoteProperty') {
            continue
        }

        if ([string]::IsNullOrWhitespace($Prefix)) {
            $pre = $property.Name
        }
        else {
            $pre = "$($Prefix)$($Delimiter)$($property.Name)"
        }

        # Handle PSCustomObject
        [string] $fullName = $property.Value.GetType().FullName
        if ($fullName -eq 'System.Management.Automation.PSCustomObject') {
            Flatten-JsonHelper -JsonObject $property.Value `
                -Delimiter $Delimiter `
                -Prefix $pre `
                -HashTable $HashTable
        }
        # Handle Object
        elseif ($fullName -eq 'System.Object[]') {
            $valArr = $property.Value
            # Handle empty objects
            if([string]::IsNullOrEmpty($valArr)) {
              $HashTable.Add($pre, $property.Value)
            }
            else {
              for ($i = 0; $i -lt $valArr.Length; $i++) {
                  Flatten-JsonHelper -JsonObject $valArr[$i] `
                      -Delimiter $Delimiter `
                      -Prefix "$($pre)$($Delimiter)$($i)" `
                      -HashTable $HashTable
              }
            }
        }
        # Handle strings
        else {
            $HashTable.Add($pre, $property.Value)
        }
    }
}