Support key signing and handle dry_run cleaner

[Marenz]

• Support key signing
• Consider dry_run status in dispatch merging

[llucax]

Awesome to see the support for parallel dry-run actors! 🎉

Next time maybe split the deprecation of key in favor of auth_key in a separate commit, as it was sometimes confusing to have it mixed with the introduction of signing.

[Copilot]

Pull Request Overview

This PR adds support for key signing and improves dry_run handling in the dispatch system. The changes introduce new authentication parameters and ensure that dispatches with different dry_run statuses are handled separately during merging operations.

• Add support for key signing with new sign_secret parameter and deprecate key in favor of auth_key
• Modify merge strategies to consider dry_run status when grouping dispatches
• Update dependency version for frequenz-client-dispatch

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/frequenz/dispatch/_dispatcher.py	Add new authentication parameters (auth_key, sign_secret) and deprecate key parameter
src/frequenz/dispatch/_merge_strategies.py	Include dry_run status in merge identity functions for both merge strategies
tests/test_managing_actor.py	Update test client to support new authentication parameters
tests/test_frequenz_dispatch.py	Add test to verify dry_run dispatches are not merged together
pyproject.toml	Update frequenz-client-dispatch dependency version
RELEASE_NOTES.md	Document new features and deprecation notice

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[Copilot]

The assertion logic doesn't match the validation in the actual Dispatcher class. The Dispatcher raises ValueError when both are provided or neither are provided, but this test only checks that at least one is provided. Consider aligning the test validation with the production code logic.

Suggested change

	assert key or auth_key
	# Ensure exactly one of key or auth_key is provided, matching Dispatcher logic
	assert (key is not None) != (auth_key is not None)

[llucax]

Just a couple of nitpick comments.

[llucax]

It just occurred to me, but you could also use overloads to ensure this is called correctly when type-checking:

    @overload
    def __init__(
        self,
        *,
        microgrid_id: MicrogridId,
        server_url: str,
        key: str,
        auth_key: None = None,
        sign_secret: str | None = None,
        call_timeout: timedelta = timedelta(seconds=60),
        stream_timeout: timedelta = timedelta(minutes=5),
    ):
    @overload
    def __init__(
        self,
        *,
        microgrid_id: MicrogridId,
        server_url: str,
        key: None = None,
        auth_key: str,
        sign_secret: str | None = None,
        call_timeout: timedelta = timedelta(seconds=60),
        stream_timeout: timedelta = timedelta(minutes=5),
    ):

But might be overkill for this.