Dapper and MongoDB IKeyValueStore: atomic TryDeleteAsync overrides for legacy-pause adoption (elsa-core#8529) #260

3.9 blocker. This is required to close elsa-core#8529 for the Dapper and MongoDB providers. Approved by Crew Lead as option A.

Problem

elsa-core #8538 (main) and #8539 (release/3.9.0) add IKeyValueStore.TryDeleteAsync as a default interface method. The default implementation finds the row and then deletes it, so it is not atomic. When two nodes adopt the same legacy pause (the legacy key elsa.quiescence.pause.{shell} moving to the host-wide key in QuiescenceSignal.SweepAndAdoptLegacyPauseAsync), both nodes can find the row, both can delete it, and both get true. Both then save the host key, so a pause that an operator cleared in between can be resurrected (#8529).

The EF Core and in-memory stores override the method atomically. The Dapper and MongoDB key-value stores fall back to the default, which leaves the blocker open for those providers.

Scope

• Bump ElsaVersion to a core preview that contains the method (post-#8529). This bump is needed for the ext 3.9 rebuild anyway.
• Dapper KeyValueStore: override with a single tenant-filtered DELETE and return whether it affected any rows:
  TryDeleteAsync => (await store.DeleteAsync(q => q.Is(nameof(KeyValuePairRecord.Id), key), ct)) > 0
• MongoDB KeyValueStore: override with DeleteOneAsync(store.ApplyTenantScope(Builders<SerializedKeyValuePair>.Filter.Eq(x => x.Key, key))) and return DeletedCount > 0.
  Do not use MongoDbStore.DeleteWhereAsync. It finds the rows, then runs DeleteMany, and returns the number it found rather than DeletedCount, so it isn't atomic.
• Tests: a two-node test where only one TryDeleteAsync returns true for the same key, for Dapper (SQLite) and for Mongo (Testcontainers).
• Note: Dapper's strict tenant filter doesn't match NULL legacy rows under the default tenant (Dapper Store: SetTenantId overwrites every TenantId (incl. "*"), key-only upserts allow cross-tenant overwrite, and reads have no "*" visibility #245). Confirm how adoption behaves for default-tenant legacy rows, and document any gap. The Dapper Store: SetTenantId overwrites every TenantId (incl. "*"), key-only upserts allow cross-tenant overwrite, and reads have no "*" visibility #245 fix itself stays on 3.10.

Refs

elsa-core #8529, #8538, #8539; elsa-extensions #245.