Add trace activity-buffering logic when DeliveryMode is "expectReplies"

[stevengum]

Fixes #2732

FYI @alopix, @johnataylor, @EricDahlvang

Description

When DeliveryMode is "expectReplies", outgoing trace activities are not routed through the TurnContext's BotAdapter. This resulted in trace activities being sent to the channel. This PR duplicates the trace activity logic in BotFrameworkAdapter.sendActivities() and places it in TurnContext.sendActivities().

BotFrameworkAdapter.sendActivities():

botbuilder-js/libraries/botbuilder/src/botFrameworkAdapter.ts

Lines 979 to 981 in 015ebb7

	if (activity.type === 'trace' && activity.channelId !== 'emulator') {
	// Just eat activity
	responses.push({} as ResourceResponse);

There are a couple of ways to address issue #2732, including via BotFrameworkAdapter.processActivity() or SkillDialog/BeginSkill. This current implementation at 02aff60 is perhaps the most straightforward way of fixing it, but may have unintended consequences for channels with custom clients/3rd-party channels that do support trace activities.

Additionally, having the trace filtering logic in BotFrameworkAdapter.processActivity() means the "restriction" is at the same level (an integration library, botbuilder) as opposed to having the logic in a base concept library (botbuilder-core).

Specific Changes

• Move away from magic strings in BotFrameworkAdapter.sendActivities()
• Duplicate trace activity logic in TurnContext.sendActivities()
• Add unit tests for TurnContext changes & minor test cleanup

Testing

Added unit tests

[coveralls]

Pull Request Test Coverage Report for Build 170414

• 7 of 7 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.07%) to 83.409%

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Totals
Change from base Build 170396:	0.07%
Covered Lines:	15599
Relevant Lines:	17788

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💛 - Coveralls

[stevengum]

@gabog, right now I strongly believe we should add expectReplies bufferedReplies-parsing logic at the BotFrameworkAdapter level. We should also setup the Adapter to have a hook for filtering out certain activities in bufferedReplies and configure tracing to be an explicit opt-in.

[joshgummersall]

@stevengum do we intend to land this change? I see it's linked to an open R11 issue.

[stevengum]

Yes, this will probably land early next week. I'll sync with @gabog and @tracyboehrer to verify resource availability for porting it to .NET and Python

[joshgummersall]

This seems okay to me, though I don't think I fully understand the potential issues you mentioned in the description.

[joshgummersall]

Tiny suggestion, otherwise LGTM.