What should trigger the Telegram notification?

[frgfm]

As mentioned in #412, we might have a bad pattern for Telegram notifications

Currently we send this when a detection is created (cf. https://github.com/pyronear/pyro-api/blob/main/src/app/api/api_v1/endpoints/detections.py#L136)

I suggest we update this to only send one if a sequence is created (https://github.com/pyronear/pyro-api/blob/main/src/app/api/api_v1/endpoints/detections.py#L117). And the question now is whether we should send a notification when a new detection is addded to an existing sequence.

What do you think?