No notification alerts sent due to 400 Bad Request error

### Current Behavior:
Dependency-Track is not able to send mattermost notification (400 Bad Request)
### Steps to Reproduce:

1- Start Dependency-Track in a docker container with the "DEBUG" log level and login
2- From Projects, create a project named "test"
3- Go to "Administation", go to "Notifications" then "Alerts", create a new alert called "alert1" and choose "webhook" as publisher
4- Click on the "alert1" and update it by setting your "webhook URL" and by checking all options in "Group"
5- Go back to your "test" project and updoad a BOM file "bom.xml" containing some vulnerabilities
6- Logs are showing:
An error was encountered publishing notification to mattermost
HTTP Status : 400 Bad Request

### Expected Behavior:
Dependency-Track should be able to send the notification server

### Environment:

- Dependency-Track Version: v4.4.1
- Distribution: Helm charts , evryfs-oss/dependency-track
- BOM Format & Version:
- Database Server: PostgreSQL
- Browser:

### Additional Details:
I can able to send test message to matter most channel using curl command.

2022-03-09 05:45:42,568 INFO [BomUploadProcessingTask] Processing CycloneDX BOM uploaded to project: 66e751d4-ebc2-4fb7-9e12-6c05f4f75c83
2022-03-09 05:45:43,837 ERROR [WebhookPublisher] An error was encountered publishing notification to Outbound Webhook
2022-03-09 05:45:43,838 ERROR [WebhookPublisher] HTTP Status : 400 Bad Request
2022-03-09 05:45:43,838 ERROR [WebhookPublisher] Destination: