POST Message to Teams Channel with Application-only Permissions Not Allowed for Regular Use Cases

Start with the GraphServiceClient Java example in the issue and the linked Microsoft Teams import-messages documentation. Verify the documented constraints for application-only channel-message POST requests and the available delegated-authentication options for headless services. Done means documenting a supported authentication path or confirming that no supported workaround exists.

Is your feature request related to a problem? Please describe the problem.

Hello,
I am attempting to use the Microsoft Graph API to send messages to a Microsoft Teams channel using application-only authentication with the following code:

import com.azure.identity.ClientSecretCredential;
import com.azure.identity.ClientSecretCredentialBuilder;
import com.microsoft.graph.models.ChatMessage;
import com.microsoft.graph.models.ItemBody;
import com.microsoft.graph.serviceclient.GraphServiceClient;

public class GraphClientExample {
    public static void main(String[] args) throws Exception {

        final String clientId = "****-2189-4dab-a9b8-28dc0f57b181";
        final String tenantId = "****-4b22-4755-a153-421da388048a";
        final String clientSecret = "F1p8Q~**************";

        final String[] scopes = new String[] { "https://graph.microsoft.com/.default" };

        final ClientSecretCredential credential = new ClientSecretCredentialBuilder()
                .clientId(clientId).tenantId(tenantId).clientSecret(clientSecret).build();

        if (null == scopes || null == credential) {
            throw new Exception("Unexpected error");
        }

        final GraphServiceClient graphClient = new GraphServiceClient(credential, scopes);

        ChatMessage chatMessage = new ChatMessage();
        ItemBody body = new ItemBody();
        body.setContent("Hello World");
        chatMessage.setBody(body);
        ChatMessage result = graphClient.teams().byTeamId("459b419d-9d5e-42cd-b59d-*********").channels().byChannelId("19%********************Gu3neGtMFiU8PSRzeaR-uL5AWU1%40thread.tacv2").messages().post(chatMessage);
    }
}

However, I am encountering the following error:
Message POST is allowed in application-only context only for import purposes. Refer to https://docs.microsoft.com/microsoftteams/platform/graph-api/import-messages/import-external-messages-to-teams for more details.
From what I understand, the Microsoft Teams API restricts POST requests in the application-only context to migration or import purposes. This means I am unable to use application-only authentication to send messages to a Teams channel.

Question:

Is there a recommended way to send messages to Microsoft Teams channels using application-only authentication in scenarios other than data migration?
If delegated permissions are required, is there an alternative method to authenticate using delegated permissions in a headless application or server environment?
Any insights or workarounds would be greatly appreciated!

Thank you!

Describe the solution you'd like.

Question:

Is there a recommended way to send messages to Microsoft Teams channels using application-only authentication in scenarios other than data migration?
If delegated permissions are required, is there an alternative method to authenticate using delegated permissions in a headless application or server environment?
Any insights or workarounds would be greatly appreciated!

Additional context?

No response