Allow configurable integration auto-assign per project

[apollo13]

I'd like to add a setting to project which configures the auto assignment of integrations to all available checks. It could be a simple boolean on the project settings page. Would you like to see that feature?

[cuu508]

Thanks for the suggestion.

I'd like to avoid adding modes to interfaces as much as possible, so I've been thinking about alternatives.

The Management API users can already specify a channels key when creating a new check, so they can set the default value on the client side.

For Ping API, and auto-provisioning, the "should we assign all integrations" flag could perhaps go in the URL:

# If a check with slug "sample-slug" does not exist, create it and assign all channels 
GET /sample-ping-key/sample-slug/?create=1

# If a check with slug "sample-slug" does not exist, create it but do not assign any channels
GET /sample-ping-key/sample-slug/?create=1&channels=

(and perhaps more configuration options could go there in future)

For the web interface, we could add a checkbox in the "Add Check" dialog. Checked by default to match the current default, but the user can uncheck it:

[apollo13]

Ah yes, a checkbox there would do. There is another instance though where such a checkbox would probably be useful, namely when creating an integration/channel it is assigned to all checks as well:
https://github.com/apollo13/healthchecks/blob/e546a1325ba04a2c74ea16accae8ed79b2185505/hc/front/views.py#L1284

Since this affects existing checks I'd like to have a way to prevent that as well (a checkbox would do I guess).