function ConvertTo-Base64($string) {
    $bytes  = [System.Text.Encoding]::UTF8.GetBytes($string);
    $encoded = [System.Convert]::ToBase64String($bytes);
    return $encoded;
}

function Get-HttpBasicHeader([string]$username, [string]$password, $Headers = @{}) {
    $b64 = ConvertTo-Base64 "$($username):$($Password)"
    $Headers["Authorization"] = "Basic $b64"
    $Headers["X-Atlassian-Token"] = "nocheck"
    return $Headers
}

function add_comment([string]$issueKey,[string]$comment) {
    $body = ('{"body": "'+$comment+'"}')
    $comment=(Invoke-RestMethod -uri ($restapiuri +"issue/$issueKey/comment") -Headers $headers -Method POST -ContentType "application/json" -Body $body).id    
    return $comment
}


$restapiuri = "https://jira.server.com/rest/api/2/"
$headers = Get-HttpBasicHeader "user" "password"

add_comment "MyIssue-1234" "[~test.user] please handle the issue."