Anthropic chat model doesn't return the "finish reason" when in streaming mode

[ThomasVitale]

Bug description
When calling the Anthropic chat model in a blocking way, the final completion comes with an "end_turn" finish reason. The same is not true when using the streaming mode (the finishReason field is null).

Environment
Spring AI 1.0.0-SNAPSHOT

Steps to reproduce
See this auto-tests which demonstrate the difference:

spring-ai/models/spring-ai-anthropic/src/test/java/org/springframework/ai/anthropic/AnthropicChatModelObservationIT.java

Line 146 in 6c32c82

.hasHighCardinalityKeyValue(HighCardinalityKeyNames.RESPONSE_FINISH_REASONS.asString(), finishReasons)

Expected behavior
The same finish reason ("end_turn") is returned both when using the blocking and streaming option.