OpenAI v1 Completions API

[tgaddair]

Related: #145.

Does not implement chat completions with templates. This will be done in a follow-up.

Python:

from openai import OpenAI

openai_api_key = "EMPTY"
openai_api_base = "http://127.0.0.1:8080/v1"
client = OpenAI(
    api_key=openai_api_key,
    base_url=openai_api_base,
)

# synchrounous completions
completion = client.completions.create(
    model=adapter_id,
    prompt=prompt,
)
print("Completion result:", completion[0].choices[0].text)

# streaming completions
completion_stream = client.completions.create(
    model=adapter_id,
    prompt=prompt,
    stream=True,
)

for message in completion_stream:
    print("Completion message:", message)

REST:

curl http://127.0.0.1:8080/v1/completions \
-H "Content-Type: application/json" \
-d '{
"model": "",
"prompt": "Instruct: Write a detailed analogy between mathematics and a lighthouse.\nOutput:",
"max_tokens": 100
}'

Note that the model param is used in place of the adapter_id in LoRAX. So specifying model="" uses the base model, while model="Yhyu13/phi-2-sft-alpaca_gpt4_en-ep1-lora" would use the given adapter.