fixes tests & move braintrust api_keys to request headers (#535)

# What does this PR do?

- braintrust scoring provider requires OPENAI_API_KEY env variable to be
set
- move this to be able to be set as request headers (e.g. like together
/ fireworks api keys)
- fixes pytest with agents dependency

## Test Plan

**E2E**
```
llama stack run 
```
```yaml
scoring:
  - provider_id: braintrust-0
    provider_type: inline::braintrust
    config: {}
```

**Client**
```python
self.client = LlamaStackClient(
    base_url=os.environ.get("LLAMA_STACK_ENDPOINT", "http://localhost:5000"),
    provider_data={
        "openai_api_key": os.environ.get("OPENAI_API_KEY", ""),
    },
)
```
- run `llama-stack-client eval run_scoring`

**Unit Test**
```
pytest -v -s -m meta_reference_eval_together_inference eval/test_eval.py
```

```
pytest -v -s -m braintrust_scoring_together_inference scoring/test_scoring.py --env OPENAI_API_KEY=$OPENAI_API_KEY
```
<img width="745" alt="image"
src="https://github.com/user-attachments/assets/68f5cdda-f6c8-496d-8b4f-1b3dabeca9c2">

## Before submitting

- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [ ] Ran pre-commit to handle lint / formatting issues.
- [ ] Read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [ ] Updated relevant documentation.
- [ ] Wrote necessary unit or integration tests.

llama_stack/providers/inline/scoring/braintrust/__init__.py

@@ -6,10 +6,15 @@
 from typing import Dict
 
 from llama_stack.distribution.datatypes import Api, ProviderSpec
+from pydantic import BaseModel
 
 from .config import BraintrustScoringConfig
 
 
+class BraintrustProviderDataValidator(BaseModel):
+    openai_api_key: str
+
+
 async def get_provider_impl(
     config: BraintrustScoringConfig,
     deps: Dict[Api, ProviderSpec],

llama_stack/providers/inline/scoring/braintrust/braintrust.py

@@ -12,9 +12,11 @@ from llama_stack.apis.common.type_system import *  # noqa: F403
 from llama_stack.apis.datasetio import *  # noqa: F403
 from llama_stack.apis.datasets import *  # noqa: F403
 
-# from .scoring_fn.braintrust_scoring_fn import BraintrustScoringFn
+import os
+
 from autoevals.llm import Factuality
 from autoevals.ragas import AnswerCorrectness
+from llama_stack.distribution.request_headers import NeedsRequestProviderData
 from llama_stack.providers.datatypes import ScoringFunctionsProtocolPrivate
 
 from llama_stack.providers.utils.scoring.aggregation_utils import aggregate_average
@@ -24,7 +26,9 @@ from .scoring_fn.fn_defs.answer_correctness import answer_correctness_fn_def
 from .scoring_fn.fn_defs.factuality import factuality_fn_def
 
 
-class BraintrustScoringImpl(Scoring, ScoringFunctionsProtocolPrivate):
+class BraintrustScoringImpl(
+    Scoring, ScoringFunctionsProtocolPrivate, NeedsRequestProviderData
+):
     def __init__(
         self,
         config: BraintrustScoringConfig,
@@ -79,12 +83,25 @@ class BraintrustScoringImpl(Scoring, ScoringFunctionsProtocolPrivate):
                     f"Dataset {dataset_id} does not have a '{required_column}' column of type 'string'."
                 )
 
+    async def set_api_key(self) -> None:
+        # api key is in the request headers
+        if self.config.openai_api_key is None:
+            provider_data = self.get_request_provider_data()
+            if provider_data is None or not provider_data.openai_api_key:
+                raise ValueError(
+                    'Pass OpenAI API Key in the header X-LlamaStack-ProviderData as { "openai_api_key": <your api key>}'
+                )
+            self.config.openai_api_key = provider_data.openai_api_key
+
+        os.environ["OPENAI_API_KEY"] = self.config.openai_api_key
+
     async def score_batch(
         self,
         dataset_id: str,
         scoring_functions: List[str],
         save_results_dataset: bool = False,
     ) -> ScoreBatchResponse:
+        await self.set_api_key()
         await self.validate_scoring_input_dataset_schema(dataset_id=dataset_id)
         all_rows = await self.datasetio_api.get_rows_paginated(
             dataset_id=dataset_id,
@@ -105,6 +122,7 @@ class BraintrustScoringImpl(Scoring, ScoringFunctionsProtocolPrivate):
     async def score_row(
         self, input_row: Dict[str, Any], scoring_fn_identifier: Optional[str] = None
     ) -> ScoringResultRow:
+        await self.set_api_key()
         assert scoring_fn_identifier is not None, "scoring_fn_identifier cannot be None"
         expected_answer = input_row["expected_answer"]
         generated_answer = input_row["generated_answer"]
@@ -118,6 +136,7 @@ class BraintrustScoringImpl(Scoring, ScoringFunctionsProtocolPrivate):
     async def score(
         self, input_rows: List[Dict[str, Any]], scoring_functions: List[str]
     ) -> ScoreResponse:
+        await self.set_api_key()
         res = {}
         for scoring_fn_id in scoring_functions:
             if scoring_fn_id not in self.supported_fn_defs_registry:

llama_stack/providers/inline/scoring/braintrust/config.py

@@ -6,4 +6,8 @@
 from llama_stack.apis.scoring import *  # noqa: F401, F403
 
 
-class BraintrustScoringConfig(BaseModel): ...
+class BraintrustScoringConfig(BaseModel):
+    openai_api_key: Optional[str] = Field(
+        default=None,
+        description="The OpenAI API Key",
+    )