Add API-specific sections to the CONTRIBUTING template

Because of the protocol buffers stuff, the API repos need a few more
instructions on how to contribute.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

cookiecutter/{{cookiecutter.github_repo_name}}/CONTRIBUTING.md

@@ -10,13 +10,38 @@ python -m build
 ```
 
 ## Local development
+{%- if cookiecutter.type == "api" %}
+
+You need to make sure you have the `git submodules` updated:
+
+```sh
+git submodule update --init
+```
+
+### Running protolint
+
+To make sure some common mistakes are avoided and to ensure a consistent style
+it is recommended to run `protolint`. After you [installed
+`protolint`](https://github.com/yoheimuta/protolint#installation), just run:
+
+```sh
+protolint lint proto
+```
+
+### Python setup
+{%- endif %}
 
 You can use editable installs to develop the project locally (it will install
 all the dependencies too):
 
 ```sh
 python -m pip install -e .
 ```
+{%- if cookiecutter.type == "api" %}
+
+This will also generate the Python files from the `proto/` files and leave them
+in `py/`, so you can inspect them.
+{%- endif %}
 
 Or you can install all development dependencies (`mypy`, `pylint`, `pytest`,
 etc.) in one go too:
@@ -34,6 +59,31 @@ nox
 
 You can also use `nox -R` to reuse the current testing environment to speed up
 test at the expense of a higher chance to end up with a dirty test environment.
+{%- if cookiecutter.type == "api" %}
+
+### Upgrading dependencies
+
+If you want to update the dependency `frequenz-api-common`, then you need to:
+
+1. Update the submodule `frequenz-api-common`
+2. Update the version of the `frequenz-api-common` package in `pyproject.toml`
+
+The version of `frequenz-api-common` used in both places mentioned above should
+be the same.
+
+Here is an example of upgrading the `frequenz-api-common` dependency to version
+`v0.2.0`:
+```sh
+ver="0.2.0"
+
+cd submodules/frequenz-api-common
+git remote update
+git checkout v${ver}
+cd -
+
+sed s/"frequenz-api-common == [0-9]\.[0-9]\.[0-9]"/"frequenz-api-common == ${ver}"/g -i pyproject.toml
+```
+{%- endif %}
 
 ### Running tests / checks individually
 
@@ -67,9 +117,9 @@ These are the steps to create a new release:
 1. Get the latest head you want to create a release from.
 
 2. Update the `RELEASE_NOTES.md` file if it is not complete, up to date, and
-   clean from 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
+   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.
 
 3. Create a new signed tag using the release notes and