Use SendInBlue to send confirmation mail with an activation link (use a SendInBlue template ID)

SendInBlue_ConfirmationEmail.cs

public static bool SendConfirmationEmail(string emailAddress, string activationLink)
{
    var client = new RestClient("https://api.sendinblue.com/v3/smtp/email");
    var sendInBlueRequest = new RestRequest(Method.POST);
    sendInBlueRequest.AddHeader("api-key", "SENDINBLUE_API_KEY");
    sendInBlueRequest.AddHeader("Accept", "application/json");
    sendInBlueRequest.AddHeader("Content-Type", "application/json");
    sendInBlueRequest.AddParameter("undefined", $"{{\"tags\":[\"Activate account for {{emailAddress}}\"],\"sender\":{{\"email\":\"you@domain.tld\",\"name\":\"You\"}},\"htmlContent\":\"\",\"replyTo\":{{\"email\":\"you@domain.tld\",\"name\":\"You\"}},\"templateId\":2,\"to\":[{{\"email\":\"{emailAddress}\",\"name\":\"{emailAddress}\"}}],\"params\":{{\"ActivationLink\":\"{activationLink}\"}}}}", ParameterType.RequestBody);
    var sendInBlueResponse = client.Execute(sendInBlueRequest);
    return sendInBlueResponse.IsSuccessful;
}