Async parity: add context= kwarg to AsyncDataverseClient, fix r.json() content_type

- Add `context: Optional[OperationContext] = None` keyword argument to
  AsyncDataverseClient.__init__ with the same conflict validation and
  three-branch config initialization as the sync DataverseClient
- Update AsyncDataverseClient docstring to document the context parameter
- Add content_type=None to all await r.json() calls in _async_relationships.py
  for consistency with _async_odata.py

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Abel Milash

src/PowerPlatform/Dataverse/aio/async_client.py

@@ -10,7 +10,7 @@
 from azure.core.credentials_async import AsyncTokenCredential
 
 from .core._async_auth import _AsyncAuthManager
-from ..core.config import DataverseConfig
+from ..core.config import DataverseConfig, OperationContext
 from .data._async_odata import _AsyncODataClient
 from .operations.async_dataframe import AsyncDataFrameOperations
 from .operations.async_records import AsyncRecordOperations
@@ -43,8 +43,14 @@ class AsyncDataverseClient:
     :param config: Optional configuration for language, timeouts, and retries.
         If not provided, defaults are loaded from :meth:`~PowerPlatform.Dataverse.core.config.DataverseConfig.from_env`.
     :type config: ~PowerPlatform.Dataverse.core.config.DataverseConfig or None
+    :param context: Optional caller-defined context object appended to the
+        outbound ``User-Agent`` header for plugin/tool attribution. Cannot be used
+        together with ``config`` -- pass the context via
+        :class:`~PowerPlatform.Dataverse.core.config.DataverseConfig` instead.
+    :type context: ~PowerPlatform.Dataverse.core.config.OperationContext or None
 
     :raises ValueError: If ``base_url`` is missing or empty after trimming.
+    :raises ValueError: If both ``config`` and ``context`` are provided.
 
     .. note::
         The client lazily initializes its internal OData client on first use,
@@ -95,12 +101,24 @@ def __init__(
         base_url: str,
         credential: AsyncTokenCredential,
         config: Optional[DataverseConfig] = None,
+        *,
+        context: Optional[OperationContext] = None,
     ) -> None:
+        if config is not None and context is not None:
+            raise ValueError(
+                "Cannot specify both 'config' and 'context'. "
+                "Pass operation_context via DataverseConfig instead."
+            )
         self.auth = _AsyncAuthManager(credential)
         self._base_url = (base_url or "").rstrip("/")
         if not self._base_url:
             raise ValueError("base_url is required.")
-        self._config = config or DataverseConfig.from_env()
+        if config is not None:
+            self._config = config
+        elif context is not None:
+            self._config = DataverseConfig(operation_context=context)
+        else:
+            self._config = DataverseConfig.from_env()
         self._odata: Optional[_AsyncODataClient] = None
         self._session: Optional[aiohttp.ClientSession] = None
         self._closed: bool = False

src/PowerPlatform/Dataverse/aio/data/_async_relationships.py

@@ -144,7 +144,7 @@ async def _get_relationship(self, schema_name: str) -> Optional[Dict[str, Any]]:
         url = f"{self.api}/RelationshipDefinitions"
         params = {"$filter": f"SchemaName eq '{self._escape_odata_quotes(schema_name)}'"}
         r = await self._request("get", url, headers=await self._headers(), params=params)
-        data = await r.json()
+        data = await r.json(content_type=None)
         results = data.get("value", [])
         return results[0] if results else None
 
@@ -179,7 +179,7 @@ async def _list_relationships(
         if select:
             params["$select"] = ",".join(select)
         r = await self._request("get", url, headers=await self._headers(), params=params)
-        return (await r.json()).get("value", [])
+        return (await r.json(content_type=None)).get("value", [])
 
     async def _list_table_relationships(
         self,
@@ -246,7 +246,9 @@ async def _list_table_relationships(
         )
 
         return (
-            (await r1.json()).get("value", []) + (await r2.json()).get("value", []) + (await r3.json()).get("value", [])
+            (await r1.json(content_type=None)).get("value", [])
+            + (await r2.json(content_type=None)).get("value", [])
+            + (await r3.json(content_type=None)).get("value", [])
         )
 
     def _extract_id_from_header(self, header_value: Optional[str]) -> Optional[str]: