add nocover to protocol implementations

Author: jkeifer

src/stapi_fastapi/backends/product_backend.py

@@ -9,7 +9,7 @@
 from stapi_fastapi.routers.product_router import ProductRouter
 
 
-class ProductBackend(Protocol):
+class ProductBackend(Protocol):  # pragma: nocover
     async def search_opportunities(
         self,
         product_router: ProductRouter,

src/stapi_fastapi/backends/root_backend.py

@@ -5,7 +5,7 @@
 from stapi_fastapi.models.order import Order, OrderCollection
 
 
-class RootBackend(Protocol):
+class RootBackend(Protocol):  # pragma: nocover
     async def get_orders(self, request: Request) -> OrderCollection:
         """
         Return a list of existing orders.