Add `forecast_horizon` range to the protobuf definitions #434

Job	Run time
Build distribution packages	19s
Test with nox (ubuntu-20.04, 3.11, ci_checks_max)	1m 3s
Check proto files with protolint	11s
Test with nox (ubuntu-20.04, 3.11, pytest_min)	39s
Test documentation website generation	43s
Test package installation in different architectures	2m 5s
Test with nox	1s
Publish documentation website to GitHub pages	0s
Create GitHub release	0s
Publish packages to PyPI	0s
	5m 1s

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