add support for sending transactional in-app messages

[avigoldman]

Adds SendInAppRequest and APIClient#send_in_app for the POST /v1/send/in_app endpoint. Follows the same pattern as the existing inbox message support.

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Note

Low Risk
Low risk: adds a new send_in_app request type and API client method following existing send patterns, with no changes to existing endpoints or shared request/response handling.

Overview
Adds support for transactional in-app sends by introducing SendInAppRequest and wiring APIClient#send_in_app to call POST /v1/send/in_app with the same success/400/other error handling used by other send endpoints.

Updates the gem entrypoint (lib/customerio.rb) to require the new request type and adds API client specs covering success, validation (400), and server error (5xx) cases for send_in_app.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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New request class is exact duplicate of existing class

Low Severity

SendInAppRequest is a line-for-line duplicate of SendInboxMessageRequest — identical REQUIRED_FIELDS, OPTIONAL_FIELDS, initialize, invalid_field?, and an unused encode method. If a bug is fixed in one class it could easily be missed in the other. A shared base class or module mixin would eliminate this duplication.

 

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