fix(workflow): Workflow Activation Encoder was discarding SDK flags

[mjameswh]

What was changed

• The logic that applies payload encoding on Workflow Activation Completions was missing some object spread operators, causing lang's SDK flags to be discarded. This PR fixes that logic.

• Introduced a mechanism that allows retroactively enabling SDK Flags on Workflow Task being replayed, based on the SDK version that produced that originally processed the WFT.

Why?

• Due to SDK flags not being properly recorded to the Workflow Task, this bug would result in Non Determinism Errors on attempts to replay a Workflow where the presence or absence of a flag would effectively impact subsequent commands produced by the Workflow.

• The most common symptoms of this issue would be an NDE that involves:

  • A TimerCanceled command; or
  • A change in the ordering of some commands.

• Problematic Workflow Tasks will have been produced specifically by either TS SDK 1.11.0 or 1.11.1. Similar symptoms on Workflow Tasks emitted by other releases of the TS SDK would not be related to this bug.

• Given that existing Workflow Histories may already be affected by this omission, there's a high probability that updating Workers to an SDK release that fixes this issue would cause storms of NDEs errors, for which the only way forward would be to reset or terminate those workflows. To avoid that situation, we introduced a mechanism to retroactively enable the affected SDK Flags on WFT emitted by SDK 1.11.0 or 1.11.1.

Fixes #1533.

[ikonst]

Consider adding a comment to Activator.hasFlag to describe how flags work in that regard:

+   // During replays, sdkMetadata should dictate flags, as to respect their state in previous runs
    if (!this.info.unsafe.isReplaying && flag.default) {
      this.knownFlags.add(flag.id);
      return true;
    }

[Sushisource]

A little unfortunate to have to look at version strings, but, makes sense to me.