Apply migration from 0.18.0 to 0.19.0

=== v0.19.0 =========================================================
Script URL: https://raw.githubusercontent.com/frequenz-floss/frequenz-repo-config-python/v0.19.0/cookiecutter/migrate.py

========================================================================
Enabling exhaustive match checks for mypy...
  Updated pyproject.toml: enabled exhaustive-match
========================================================================

========================================================================
Removing default `-vv` from pytest addopts...
  Updated pyproject.toml: removed default `-vv` from [tool.pytest.ini_options]
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Removing the dummy DCO merge-queue workflow...
  Removed .github/workflows/dco-merge-queue.yml
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Pinning the DCO check in the 'Protect version branches' ruleset...
  Ruleset 'Protect version branches' is already up to date
========================================================================

========================================================================
Updating pinned build dependencies...
  Skipped pyproject.toml: build dependencies already up to date
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Enabling asyncio debug mode for pytest...
  Updated pyproject.toml: enabled asyncio debug mode under [tool.pytest.ini_options]
========================================================================

========================================================================
Updating the release instructions in CONTRIBUTING.md...
  Updated CONTRIBUTING.md: refreshed the release instructions
========================================================================

       ✅ Migration script finished successfully ✅



The migration completed successfully.

Applied-by: frequenz-floss/gh-action-dependabot-migrate

Author: frequenz-auto-dependabot[bot]

.github/workflows/dco-merge-queue.yml

@@ -53,7 +53,7 @@ Or you can use `nox`:
 nox -R -s pytest -- tests/test_*.py
 ```
 
-The same appliest to `pylint` or `mypy` for example:
+The same applies to `pylint` or `mypy` for example:
 
 ```sh
 nox -R -s pylint -- tests/test_*.py
@@ -121,12 +121,19 @@ These are the steps to create a new release:
 
 1. Get the latest head you want to create a release from.
 
+   If you use milestones, check that the milestone for this release has no open
+   issues left, and move whatever won't make it to a later milestone.
+
 2. Update the `RELEASE_NOTES.md` file if it is not complete, up to date, and
-   remove template comments (`<!-- ... ->`) and empty sections. Submit a pull
+   remove template comments (`<!-- ... -->`) and empty sections. Submit a pull
    request if an update is needed, wait until it is merged, and update the
    latest head you want to create a release from to get the new merged pull
    request.
 
+   This can't be left for later: the notes published with the release are read
+   from the `RELEASE_NOTES.md` committed at the tagged commit, not from the tag
+   message.
+
 3. Create a new signed tag using the release notes and
    a [semver](https://semver.org/) compatible version number with a `v` prefix,
    for example:
@@ -135,6 +142,10 @@ These are the steps to create a new release:
    git tag -s --cleanup=whitespace -F RELEASE_NOTES.md v0.0.1
    ```
 
+   The signature is not optional: the *Protect released tags* ruleset rejects
+   unsigned tags. It also forbids updating or deleting a released tag, so make
+   sure you are tagging the commit you want.
+
 4. Push the new tag.
 
 5. A GitHub action will test the tag and if all goes well it will create
@@ -153,4 +164,7 @@ These are the steps to create a new release:
    Commit the new release notes and create a PR (this step should be automated
    eventually too).
 
-7. Celebrate!
+7. If you use milestones, close the milestone for this release, and create the
+   next one if it doesn't exist yet.
+
+8. Celebrate!

CONTRIBUTING.md

@@ -185,13 +185,14 @@ filterwarnings = [
   # chars as this is a regex
   'ignore:Protobuf gencode version .*exactly one major version older.*:UserWarning',
 ]
-addopts = "-vv"
 testpaths = ["tests", "src"]
+asyncio_debug = true
 asyncio_mode = "auto"
 asyncio_default_fixture_loop_scope = "function"
 required_plugins = ["pytest-asyncio", "pytest-mock"]
 
 [tool.mypy]
+enable_error_code = ["exhaustive-match"]
 explicit_package_bases = true
 namespace_packages = true
 # This option disables mypy cache, and it is sometimes useful to enable it if