Pin grpc related dependencies (#241)

We can't use wide dependencies because otherwise when building the
wheel, the latest version is used, but the generate code should use the
minimum supported version for the generation, not the latest one. See:
https://protobuf.dev/support/cross-version-runtime-guarantee/

Author: llucax

RELEASE_NOTES.md

@@ -1,10 +1,5 @@
 # Frequenz Common API Release Notes
 
-## Summary
+## Bug Fixes
 
-This release adds a new component category `COMPONENT_CATEGORY_HVAC` to the API.
-
-## New Features
-
-- A new component category `COMPONENT_CATEGORY_HVAC` has been added to the API
-  to represent HVAC (Heating, Ventilation, and Air Conditioning) systems.
+- Fix a dependency issue by pinning the `grpcio` version and related libraries.

pyproject.toml

@@ -6,6 +6,13 @@ requires = [
   "setuptools == 68.1.0",
   "setuptools_scm[toml] == 7.1.0",
   "frequenz-repo-config[api] == 0.9.2",
+  # We need to pin the protobuf, grpcio and  grpcio-tools dependencies to make
+  # sure the code is generated using the minimum supported versions, as older
+  # versions can't work with code that was generated with newer versions.
+  # https://protobuf.dev/support/cross-version-runtime-guarantee/#backwards
+  "protobuf == 4.25.3",
+  "grpcio-tools == 1.51.1",
+  "grpcio == 1.51.1",
 ]
 build-backend = "setuptools.build_meta"
 
@@ -25,7 +32,15 @@ classifiers = [
   "Typing :: Typed",
 ]
 requires-python = ">= 3.11, < 4"
-dependencies = ["grpcio >= 1.51.1, < 2", "protobuf >= 4.25.3, < 6"]
+dependencies = [
+  # We can't widen beyond 6 because of protobuf cross-version runtime guarantees
+  # https://protobuf.dev/support/cross-version-runtime-guarantee/#major
+  "protobuf >= 4.25.3, < 6", # Do not widen beyond 6!
+  # We couldn't find any document with a spec about the cross-version runtime
+  # guarantee for grpcio, so unless we find one in the future, we'll assume
+  # major version jumps are not compatible
+  "grpcio >= 1.51.1, < 2", # Do not widen beyond 2!
+]
 dynamic = ["version"]
 
 [[project.authors]]