Indicate whether the frequency plan is applicable to gateways

[halimi]

Summary

References: TheThingsNetwork/lorawan-frequency-plans#41

Extended the FrequencyPlanDescription struct with Gateways field to indicate that the frequency plan is relevant for a gateway.
Added GatewaysOnly flag to the ListFrequencyPlans RPC to filter out non-gateway related plans.

Changes

• Extended the FrequencyPlanDescription struct with Gateways field to indicate that the frequency plan is relevant for a gateway
• Added GatewaysOnly flag to the ListFrequencyPlans RPC to filter out non-gateway related plans
• Added gateways-only flag to the list-frequency-plans CLI command to filter out non-gateway related plans

Testing

Steps

• Use the gateways-only flag on the list-frequency-plans CLI command to filter out non-gateway related frequency plans

$ go run ./cmd/ttn-lw-cli gateways list-frequency-plans --gateways-only

Results

• It shows only the frequency plans where the gateways filed is true

Regressions

• No regression

Notes for Reviewers

• No notes

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• Testing: The steps/process to test this feature are clearly explained including testing for regressions.
• Infrastructure: If infrastructural changes (e.g., new RPC, configuration) are needed, a separate issue is created in the infrastructural repositories.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.

[KrishnaIyer]

Today is the merge deadline but I won't have time to review this unfortunately. Moving the milestone.

[KrishnaIyer]

Great