Api report custom header add role

  public async Task<ActionResult> GetReportEmbedded()
        {
            // Create a user password credentials.
            var accessToken = await GetTokenCredentials();

            var tokenCredentials = new TokenCredentials(accessToken, "Bearer");

            // Generate Embed Token.

            //using (FileStream fileStream = new FileStream(powerBi.Value.pbixPath, FileMode.Open, FileAccess.Read))
            using (var client = new PowerBIClient(new Uri(powerBi.Value.ApiUrl), tokenCredentials))
            using (Task<Group> tableTalkGroup = client.Groups.GetGroupsWithHttpMessagesAsync()
                .ContinueWith(task => task.Result.Body.Value.First(group => @group.Name == "*** group name ***")))
            using (Task<Report> reportTask = client.Reports.GetReportsInGroupWithHttpMessagesAsync((await tableTalkGroup).Id).ContinueWith(task => task.Result.Body.Value.First(report => report.Name == "Power BI Template")))

            {
                Dictionary<string, List<string>> headerDictionary = new Dictionary<string, List<string>>();
                headerDictionary.Add("roles", new List<string>{ "***custom role***" });

                var tokenResponse = await client.Reports.GenerateTokenInGroupWithHttpMessagesAsync(
                    (await tableTalkGroup).Id, (await reportTask).Id, new GenerateTokenRequest(accessLevel: "view"),
                    headerDictionary, CancellationToken.None);
                // Generate Embed Configuration.
                var embedConfig = new EmbedConfig()
                {
                    EmbedToken = tokenResponse.Body,
                    EmbedUrl = (await reportTask).EmbedUrl,
                    Id = (await reportTask).Id
                };

                return View(embedConfig);
            }
        }

i have uploaded a pbix file with custom role now i am trying to apply this role to the embedded report but i don't know how to add the custom header properly to add my request for the role. the ONLY reference i could find to this is here https://docs.microsoft.com/en-ca/azure/power-bi-workspace-collections/app-token-flow 

but it references the deprecated "Power BI Workspace Collections". i keep seeing the customHeader Parameter in a lot of the calls i use but i don't know how to properly use it.

i am trying to use this for my company's multi tenant solution and i want make sure customers only have access to their data. i think im going about this in the right direction but if not please let me know.