add create conversation to CloudAdapter

[johnataylor]

Fixes #5488

Also updates the abstract class to avoid casts in the application code.

[coveralls]

Pull Request Test Coverage Report for Build 251768

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 14 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.06%) to 78.908%

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Files with Coverage Reduction	New Missed Lines	%
/libraries/Microsoft.Bot.Builder/BotAdapter.cs	5	71.43%
/libraries/Microsoft.Bot.Builder/CloudAdapterBase.cs	9	72.86%

Totals
Change from base Build 251299:	0.06%
Covered Lines:	18189
Relevant Lines:	23051

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💛 - Coveralls

[stevengum]

Is there a specific reason we didn't have this method before? Or any of the CreateConversationAsync implementations in BotFrameworkAdapter?

Will this support Skills making 1:1 conversations on behalf of the host bot (e.g. in Teams)?

@johnataylor @EricDahlvang

[EricDahlvang]

@stevengum I'm not sure about Skills, but this should enable CloudAdapter in this Teams scenario: https://github.com/microsoft/BotBuilder-Samples/blob/main/samples/csharp_dotnetcore/57.teams-conversation-bot/Bots/TeamsConversationBot.cs#L150

[johnataylor]

I think it was just an omission. This improves the signature slightly. Its probably fair to say we simply don't have enough examples to make strong claims around how general any of this is. It improves the typing (removes the casts) by adding it to the abstract class and makes things more consistent. This works for Teams.

[tracyboehrer]

Is this an R14 goal? I only ask because at least for the Teams conversation sample, this would be required to get around my hack (which we could never release). I can't say whether the Composer Teams samples are on the slate for R14, so it may not matter.

[johnataylor]

Is this an R14 goal? I only ask because at least for the Teams conversation sample, this would be required to get around my hack (which we could never release). I can't say whether the Composer Teams samples are on the slate for R14, so it may not matter.

[johnataylor]

@tracyboehrer yes absolutely R14. Precisely because the gap you identified! Thanks!

[EricDahlvang]

This works for Teams. However, will this work from a skill without also exposing 'audience'? (as pointed out by @stevengum )