Allow message attachments to generate mentions
Notifications are not being generated for user names in message attachments (in my case specifically in fields) that are generated via a webhook.
STEPS TO REPRODUCE
Create a new message containing attachments/fields via a web hook. Include the name of the user in the attachment field. The name will not be recognized and tagged.
Mattermost would recognize a user's name, as defined in their notification preferences, when mentioned in a message that has an attachment/fields. Notifications would be generated for the user the same as if they are mentioned in a regular message.