hc.lib.string.replace only replaces placeholders that appear in the original template. It ignores any placeholders that "emerge" while doing string substitutions. This is done mainly to avoid unexpected behavior when check names or tags contain dollar signs.

.Webhooks can have different request bodies and headers for "up" and "events".

sendreports: use select_related() to avoid doing N queries

header storage.

services like https://ifttt.com/maker_webhooks which require a
specific content type, like application/json.

Apply the user's chosen sort order in emails also.