[api-sync 2026-07-31] gradientlabs-dotnet: split outbound conversation start into chat/email/phone

[gmtuca]

Syncs the SDK to one change in the public API: POST /outbound/conversations was removed and replaced by /outbound/conversations/chat, /email and /phone.

Outbound conversation start split per channel

Outbound.StartConversationAsync and StartOutboundConversationRequest are removed. There is now one method (and one request type) per channel, each still returning StartOutboundConversationResponse with a ConversationId.

Was	Now
StartConversationAsync with Channel = ConversationChannel.Web	StartChatConversationAsync(StartOutboundChatConversationRequest)
StartConversationAsync with Channel = ConversationChannel.Email	StartEmailConversationAsync(StartOutboundEmailConversationRequest)
StartConversationAsync with Channel = ConversationChannel.Voice	StartPhoneConversationAsync(StartOutboundPhoneConversationRequest)

Field-level migration:

Was	Now
CustomerSource	No replacement. CustomerId is always your own customer ID; third-party platform IDs go in CustomerSupportPlatformIdentifiers (Zendesk requires type zendesk_support_user, Salesforce salesforce_contact_id). The CustomerSource type is gone from the spec components and has been deleted here.
SupportPlatform optional	Required on chat and email — the highest-priority platform is no longer auto-selected. Not present at all on phone (the handler pins voice/livekit).
Channel	Encoded in the endpoint.
Subject / Body	Email only, and required together — supplying just one is rejected. Chat takes Body alone; both are optional, and the agent writes the opening message when omitted.
—	Phone adds required ToPhoneNumber and FromPhoneNumber (E.164; the from-number must already be provisioned for the company).

CustomerSupportPlatformIdentifiers and Resources are optional on all three.

Version

0.1.1 → 0.1.2 (patch — the removed endpoint has no known users, so this does not warrant a major bump), plus a CHANGELOG.md entry. No tag created or pushed.

The User-Agent version is derived from the assembly informational version, which comes from <Version>, so the two stay in step automatically — there is no separate constant to update.

Verification

dotnet build   → Build succeeded. 0 Warning(s) 0 Error(s)
dotnet test    → Passed! 76/76 (net8.0) and 76/76 (net10.0)
dotnet format --verify-no-changes → clean (exit 0)

New tests/GradientLabs.Api.Tests/OutboundTests.cs covers the three paths, required/optional field serialisation, omission of unset optionals, and API error propagation. FakeHttpMessageHandler gained LastRequestBody so tests can assert on request payloads.

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