Show unconsumed partitions in consumer groups

[jvorcak]

Summary

Previously, consumer group details only showed partitions that had a committed offset.
This PR extends the backend and frontend so all partitions are visible — including those
that have never been consumed or whose offset was deleted.

Backend

• PartitionOffsets.GroupOffset changed from int64 to *int64 — nil signals no committed offset
• Partitions without a committed offset are now included in the response (previously skipped with continue)

Frontend

• GroupPartitionOffset.groupOffset typed as number | null
• Unconsumed partitions show — for Group Offset and Lag columns
• Edit / Delete buttons on unconsumed partition rows are disabled with tooltip "No committed offset"
• Topic-level Edit / Delete buttons disabled when all partitions are unconsumed
• onEditOffsets / onDeleteOffsets at topic level only receive consumed partitions, preventing crashes in downstream modal handlers
• Lag filter (onlyShowPartitionsWithLag) updated to explicitly include unconsumed partitions rather than relying on null !== 0
• cannotEditGroupReason / cannotDeleteGroupOffsetsReason accept an optional consumedPartitions array and own the "No committed offsets" check, removing inline ternaries at call sites

Tests

• Unit test (group-details.test.tsx) covers: edit button enabled/disabled state, — rendering for unconsumed partitions
• E2E test (consumer-group-unconsumed-partitions.spec.ts) covers the full flow: produce messages, consume partially, delete an offset, verify all 3 partitions appear with correct values and button states

[Copilot]

Pull request overview

This PR updates the consumer group offsets API and the consumer group details UI to surface partitions that have no committed offsets (“unconsumed” partitions), and adds automated coverage to validate the new behavior.

Changes:

• Backend: return groupOffset: null for partitions without committed offsets and include those partitions in partitionOffsets.
• Frontend: render “—” for Group Offset / Lag when groupOffset is null, and disable per-partition edit/delete actions with a “No committed offset” tooltip.
• Tests: add unit + E2E tests to validate rendering and disabled actions for unconsumed partitions.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
frontend/tests/test-variant-console/consumers/consumer-group-unconsumed-partitions.spec.ts	Adds Playwright E2E coverage for unconsumed partitions display + disabled actions.
frontend/src/utils/tsx-utils.tsx	Extends IconButton to support data-testid for test targeting (enabled and disabled states).
frontend/src/state/rest-interfaces.ts	Updates groupOffset type to number | null to represent missing commits.
frontend/src/components/pages/consumers/modals.tsx	Avoids copying null offsets from other groups; adapts offset lookup for nullable offsets.
frontend/src/components/pages/consumers/group-details.tsx	Marks unconsumed partitions, renders “—”, and disables row actions with tooltips; adjusts filtering behavior.
frontend/src/components/pages/consumers/group-details.test.tsx	Adds unit tests ensuring disabled/enabled edit controls and “—” rendering for unconsumed partitions.
backend/pkg/console/consumer_group_offsets.go	Makes groupOffset nullable and emits partition rows even when no committed offset exists.
backend/pkg/console/consumer_group_offsets_test.go	Updates expectations for groupOffset pointer semantics.

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[r-vasquez]

LGTM, just one non-blocking minor nit. Also, if possible, let's add more context on why to the commit body or PR description please.