notify spike testing dependabot config

thoughts:

security warnings show up in top bar which is nice (https://github.com/alphagov/notifications-dependancies-dependabot/security/dependabot). this can be enabled separately to the dependency PRs, and is a one-click no-config repo setting.

i think we should probs turn the dependabot security scanning on regardless of what tool we use to manage actual dependencies

has its own page, you cant do much from there though - https://github.com/alphagov/notifications-dependancies-dependabot/network/dependencies

npm integration seems fine and works cleanly - not sure if it would update a package lock file for us though. but this just works, which is definitely not my experience with the pip stuff

it cant install pyproj and looks like it crashes as a result? eg https://github.com/alphagov/notifications-dependancies-dependabot/network/updates/304458785

it doesn't handle pip-compile nicely it looks like - got confused by some diffs. i'd like it to re-run pip compile ideally to refreeze dependencies.

we see some errors that look like git_dependencies_not_reachable {:"dependency-urls"=>["https://github.com/alphagov/notifications-utils.git"]}. From googling, this often appears to be due to repos being private. however this isn;t the case this time as utils isn't private - but i worry maybe dependabot cant process that repo (possibly due to errors similar to pyproj), and then it misinterprets errors.

We can raise support tics with github or raise issues on https://github.com/dependabot/dependabot-core/ if we have problems.