feat(opgaver): multi-tavle filter on ListOpgaver + StreamOpgaveChanges

[renemadsen]

Summary

• Replaces string tavle_id = 2; with repeated string tavle_ids = 2; on ListOpgaverRequest and StreamOpgaveChangesRequest in opgaver.proto. Same field number, type change. Hard cutover — flutter is the only consumer.
• C# handler OpgaverGrpcService.TryParseBoardIds(string) refactored to TryParseBoardIds(IEnumerable<string>) with per-entry skip-on-blank-or-non-numeric semantics + insertion-order-preserving HashSet dedup. Empty result still means "show all".
• The two consumers (ListOpgaver line 202, StreamOpgaveChanges line 780) feed the parsed list into the existing CalendarTaskRequestModel.BoardIds which BackendConfigurationCalendarService.ShouldIncludeTask already filters on (1809-1813) — no business-logic changes, only proto + glue.
• Auth gate untouched (property-level HasAccessAsync); EF schema untouched.

Why

Today the mobile home-page filter renders Checkbox widgets for tavler that visually read as multi-select, but the data model is single-select — checking a second board silently overwrites the first. This PR is the wire side of widening the model to Set<String> end-to-end. The flutter side is in a follow-up PR (linked below) that must merge in lockstep with this one (a flutter client carrying the new repeated field cannot talk to a tavle_id-only server, and vice versa).

Verification

• Pre-commit dual-subagent gate (code-review + code-simplifier) clean. Reviewer recommended ship-it; simplifier dropped fully-qualified namespaces + tightened the XML doc.
• dotnet clean && dotnet build against the embedded copy (/home/rene/Documents/workspace/microting/eform-angular-frontend/eFormAPI/Plugins/BackendConfiguration.Pn/): 0 errors, only pre-existing CS8632/NU1510 warnings.
• Backend running locally on the new DLL.
• The flutter-side feature PR will smoke-test end-to-end on device with a multi-tavler selection asserting only the chosen boards' opgaver render.

Known follow-ups (not in this PR)

• No unit tests on TryParseBoardIds or the two RPCs. Worth a backlog item: table test covering null, [], [""], [" "], ["abc"], ["1","1","2"], ["1","abc","2"].

Lockstep

• Merge order: this PR (toward stable) FIRST, then deploy the new backend, then merge the flutter-eform consumer PR.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR updates the Opgaver gRPC contract and server adapter to support filtering tasks by multiple boards (“tavler”) by widening the request field from a single tavle_id to repeated tavle_ids, and plumbing that through to the existing CalendarTaskRequestModel.BoardIds filtering.

Changes:

• Updated ListOpgaverRequest and StreamOpgaveChangesRequest in opgaver.proto to use repeated string tavle_ids = 2.
• Updated OpgaverGrpcService to read request.TavleIds in both ListOpgaver and StreamOpgaveChanges.
• Refactored TryParseBoardIds to accept IEnumerable<string>, skip blank/non-numeric entries per element, and deduplicate while preserving first-seen order.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
eFormAPI/Plugins/BackendConfiguration.Pn/BackendConfiguration.Pn/Services/GrpcServices/OpgaverGrpcService.cs	Switches request consumption to TavleIds and updates board-id parsing to handle multi-select input.
eFormAPI/Plugins/BackendConfiguration.Pn/BackendConfiguration.Pn/Protos/opgaver.proto	Updates gRPC request messages to accept multiple board IDs via repeated string tavle_ids.