Two unit tests cover the code paths introduced when email was registered
as a recognised notification provider type in Stage 2.
- TestSendExternal_EmailProviderSkipsJSONTemplate exercises the goroutine
warn path where an enabled email provider passes isDispatchEnabled but
fails supportsJSONTemplates, producing a warning log without panicking
- TestTestProvider_EmailRejectsJSONTemplateStep asserts TestProvider
returns a clear error for email providers because the JSON template
dispatch path does not apply to email delivery
Patch coverage: 6/6 changed lines covered (100%)
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