Feature/graphql table query (#486)

* Tech spec

* Object query service for Cassandra

* Gateway support for objects-query

* GraphQL query utility

* Filters, ordering

trustgraph-base/trustgraph/schema/services/__init__.py

@@ -8,4 +8,5 @@ from .config import *
 from .library import *
 from .lookup import *
 from .nlp_query import *
-from .structured_query import *
+from .structured_query import *
+from .objects_query import *

trustgraph-base/trustgraph/schema/services/objects_query.py

@@ -0,0 +1,28 @@
+from pulsar.schema import Record, String, Map, Array
+
+from ..core.primitives import Error
+from ..core.topic import topic
+
+############################################################################
+
+# Objects Query Service - executes GraphQL queries against structured data
+
+class GraphQLError(Record):
+    message = String()
+    path = Array(String())       # Path to the field that caused the error
+    extensions = Map(String())   # Additional error metadata
+
+class ObjectsQueryRequest(Record):
+    user = String()              # Cassandra keyspace (follows pattern from TriplesQueryRequest)
+    collection = String()        # Data collection identifier (required for partition key)
+    query = String()             # GraphQL query string
+    variables = Map(String())    # GraphQL variables
+    operation_name = String()    # Operation to execute for multi-operation documents
+
+class ObjectsQueryResponse(Record):
+    error = Error()              # System-level error (connection, timeout, etc.)
+    data = String()              # JSON-encoded GraphQL response data
+    errors = Array(GraphQLError()) # GraphQL field-level errors
+    extensions = Map(String())   # Query metadata (execution time, etc.)
+
+############################################################################