release of opentelemetry-collector. If you use the community contributions
  you should change the package you refer to. If you don't need them update your
  commands from `otelcontribcol` to `otelcorecol` and enjoy a 7x smaller binary.

- `services.zookeeper` has a new option `jre` for specifying the JRE to start
  zookeeper with. It defaults to the JRE that `pkgs.zookeeper` was wrapped with,
  instead of `pkgs.jre`. This changes the JRE to `pkgs.jdk11_headless` by default.

- `pkgs.pgadmin` now refers to `pkgs.pgadmin4`. `pgadmin3` has been removed.

- `pkgs.minetestclient_4` and `pkgs.minetestserver_4` have been removed, as the last 4.x release was in 2018. `pkgs.minetestclient` (equivalent to `pkgs.minetest` ) and `pkgs.minetestserver` can be used instead.

- `pkgs.noto-fonts-cjk` is now deprecated in favor of `pkgs.noto-fonts-cjk-sans`
  and `pkgs.noto-fonts-cjk-serif` because they each have different release
  schedules. To maintain compatibility with prior releases of Nixpkgs,
  `pkgs.noto-fonts-cjk` is currently an alias of `pkgs.noto-fonts-cjk-sans` and
  doesn't include serif fonts.

- `pkgs.epgstation` has been upgraded from v1 to v2, resulting in incompatible
  changes in the database scheme and configuration format.

- Some top-level settings under [services.epgstation](#opt-services.epgstation.enable)
  is now deprecated because it was redundant due to the same options being
  present in [services.epgstation.settings](#opt-services.epgstation.settings).

- The option `services.epgstation.basicAuth` was removed because basic
  authentication support was dropped by upstream.

- The option [services.epgstation.database.passwordFile](#opt-services.epgstation.database.passwordFile)
  no longer has a default value. Make sure to set this option explicitly before
  upgrading. Change the database password if necessary.

- The [services.epgstation.settings](#opt-services.epgstation.settings)
  option now expects options for `config.yml` in EPGStation v2.

- Existing data for the [services.epgstation](#opt-services.epgstation.enable)
  module would have to be backed up prior to the upgrade. To back up existing
  data to `/tmp/epgstation.bak`, run
  `sudo -u epgstation epgstation run backup /tmp/epgstation.bak`.
  To import that data after to the upgrade, run
  `sudo -u epgstation epgstation run v1migrate /tmp/epgstation.bak`

- `switch-to-configuration` (the script that is run when running `nixos-rebuild switch` for example) has been reworked
    * The interface that allows activation scripts to restart units has been streamlined. Restarting and reloading is now done by a single file `/run/nixos/activation-restart-list` that honors `restartIfChanged` and `reloadIfChanged` of the units.
        * Preferring to reload instead of restarting can still be achieved using `/run/nixos/activation-reload-list`.
    * The script now uses a proper ini-file parser to parse systemd units. Some values are now only searched in one section instead of in the entire unit. This is only relevant for units that don't use the NixOS systemd moule.
        * `RefuseManualStop`, `X-OnlyManualStart`, `X-StopOnRemoval`, `X-StopOnReconfiguration` are only searched in the `[Unit]` section
        * `X-ReloadIfChanged`, `X-RestartIfChanged`, `X-StopIfChanged` are only searched in the `[Service]` section

- The `services.bookstack.cacheDir` option has been removed, since the
  cache directory is now handled by systemd.

- The `services.bookstack.extraConfig` option has been replaced by
  `services.bookstack.config` which implements a
  [settings-style](https://github.com/NixOS/rfcs/blob/master/rfcs/0042-config-option.md)
  configuration.

- `lib.assertMsg` and `lib.assertOneOf` no longer return `false` if the passed condition is `false`, `throw`ing the given error message instead (which makes the resulting error message less cluttered). This will not impact the behaviour of code using these functions as intended, namely as top-level wrapper for `assert` conditions.