Webhook Message Search

Right now, there is no way to search for messages from webhooks based on the display name of the webhook message. This makes webhook-heavy communities (like ones that use FishingBucket, Fluxcord, Bolt, etc) difficult to moderate and search through. Currently, the only webhook-related search settings are the fields author_type and exclude_author_type, with no way to filter by the display name that goes with the webhook messages.

I propose a new field for GlobalSearchMessageRequest to include the field username or display_name. This would then be used to search through messages whose author has those names, including webhook messages. If the concern for reindexing after a username change is great, then this field could also be a webhook-only field.