Fix handling of unfinished responses from PA

[debermudez]

Previously, we were seeing SSE event responses coming back from the model that were not complete.
Complete responses would span multiple responses.
Parsing these responses would fail.
Now we check the responses and merge when necessary to enable correct parsing.

• Added fix
• Add unit test with an example offending response set.

Example failing response

{
                                "response": 'data: {"id":"8ae","object":"chat.completion.chunk","created":172,"choices":[{"index":0,"text":" seems","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":5084,"role":"assistant","content":" seems","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":" like","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":1093,"role":"assistant","content":" like","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":" you","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":499,"role":"assistant","content":" you","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":"\'re","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":2351,"role":"assistant","content":"\'re","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text"'
                            },
                            {
                                "response": ':" writing","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":4477,"role":"assistant","content":" writing","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":" a","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":264,"role":"assistant","content":" a","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":" letter","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":6661,"role":"assistant","content":" letter","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":" or","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":477,"role":"assistant","content":" or","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":" a","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":264,"role":"assistant","content":" a","tool_'
                            },
                            {
                                "response": 'calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":" passage","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":21765,"role":"assistant","content":" passage","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\ndata: {"id":"8ae835f2ecbb67f3-SJC","object":"chat.completion.chunk","created":1722875835,"choices":[{"index":0,"text":" with","logprobs":null,"finish_reason":null,"seed":null,"delta":{"token_id":449,"role":"assistant","content":" with","tool_calls":null}}],"model":"meta-llama/Llama-3-8b-chat-hf","usage":null}\n\n'
                            },

Closes #27

[nv-hwoo]

LGTM 👍