If a container unit starts on boot with a dependency on `default.target`
the image unit may start too soon, before network is ready. This cause
the unit to fail to pull the image.
- Add a dependency on `network-online.target` to make sure image pulls
don't fail.
See https://github.com/containers/podman/issues/21873
- Document the hardcoded dependency on `network-online.target` for images unit
and explain how it can be overriden if necessary.
- tests/e2e/quadlet: Add `assert-last-key-regex`
Required to test the `After=` override in [Unit] section
See https://github.com/containers/podman/pull/22057#issuecomment-2008959993
- quadlet/unitfile: add a prepenUnitLine method
Requirements on networks should be inserted at the top of the
section so the user can override them.
Signed-off-by: jbtrystram <jbtrystram@redhat.com>
