D365: Download SharePoint document, attach to Email using PowerAutomate and Azure Function

 [FunctionName("AddAttachmentToEmail")]
        public static async Task<HttpResponseMessage> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequestMessage req,
            ILogger log)
        {
var postedData = await req.Content.ReadAsStringAsync();       
            var input = JsonConvert.DeserializeObject<PowerAutomateInput>(postedData);
            if (input == null || string.IsNullOrWhiteSpace(input.EmailGUID) || string.IsNullOrWhiteSpace(input.FilePath) ||
                string.IsNullOrWhiteSpace(input.FileName))
            {
                return req.CreateResponse(HttpStatusCode.BadRequest, new
                {
                    summary = "Required Input is empty"
                });
            }

            var crmApi = await CRMWebApiHelper.GetCRMWebAPI(log);
            string sharePointAccessToken = Common.GetSharePointAccessToken();

            if (string.IsNullOrWhiteSpace(sharePointAccessToken))
            {
                return req.CreateResponse(HttpStatusCode.BadRequest, new
                {
                    summary = "Unable to get SharePoint access token."
                });
            }

            var SHAREPOINT_FILE_URL = string.Format("https://SHAREPOINTDOMAIN.sharepoint.com/sites/SITENAME/_api/Web/GetFileByServerRelativeUrl('/sites/SITENAME{0}')/$value", input.FilePath);
            var request = (HttpWebRequest)WebRequest.Create(SHAREPOINT_FILE_URL);
            request.Method = "GET";
            request.Accept = "application/json;odata=verbose";
            request.Headers.Add(HttpRequestHeader.Authorization, "Bearer " + sharePointAccessToken);
            request.ContentLength = 0;

            using (var response = request.GetResponse())
            {
                var byteArray = Common.GetByteArrayFromStream(response.GetResponseStream());
                var attachmentGUID = Common.AttachPDFDocumentToEmail(byteArray, crmApi, input.EmailGUID, input.FileName);
            }

            return req.CreateResponse(HttpStatusCode.OK, new
            {
                summary = "Request Processed"
            });
}

 public class PowerAutomateInput
    {
        public string FilePath { get; set; }

        public string EmailGUID { get; set; }

        public string FileName { get; set; }
    }

 public static byte[] GetByteArrayFromStream(Stream input)
        {
            using (var ms = new MemoryStream())
            {
                input.CopyTo(ms);
                return ms.ToArray();
            }
        }

 public static Guid AttachPDFDocumentToEmail(byte[] byteArray, CRMWebAPI crmApi, string emailId, string fileName)
        {
            var convertFileToBase64 = Convert.ToBase64String(byteArray);
            var attachmentDictionary = new Dictionary<string, object>();
            var emailObject = $"/activitypointers({emailId})";
            attachmentDictionary.Add("objectid_activitypointer@odata.bind", emailObject);
            attachmentDictionary.Add("mimetype", "application/pdf");
            attachmentDictionary.Add("objecttypecode", "email");
            attachmentDictionary.Add("body", convertFileToBase64);
            attachmentDictionary.Add("filename", fileName);
            var result = crmApi.Create("activitymimeattachments", attachmentDictionary).Result;
            return result;
        }