Err embedding when multiple relationships found

When having one-to-many relationships like:

person        -< message[sender]
person        -< message[recipient]
person_detail -< message[sender]
person_detail -< message[recipient]

Where person_detail is a view of person.

This request:

GET "/message?select=*,sender(*)"

Is ambiguous. Both person or person_detail could be embedded.

Until now we have returned the first detected relationship but
now we return a 300 Multiple Choices error with a
descriptive error message asking the user to disambiguate.

This is more helpful for the user and also aids in cases of more
complex relationships.

test/Feature/DeleteSpec.hs

@@ -37,7 +37,7 @@ spec =
         request methodDelete "/complex_items?id=eq.3&select=ciId:id::text,ciName:name" [("Prefer", "return=representation")] ""
           `shouldRespondWith` [str|[{"ciId":"3","ciName":"Three"}]|]
       it "can embed (parent) entities" $
-        request methodDelete "/tasks?id=eq.8&select=id,name,project(id)" [("Prefer", "return=representation")] ""
+        request methodDelete "/tasks?id=eq.8&select=id,name,project:projects(id)" [("Prefer", "return=representation")] ""
           `shouldRespondWith` [str|[{"id":8,"name":"Code OSX","project":{"id":4}}]|]
           { matchStatus  = 200
           , matchHeaders = ["Content-Range" <:> "*/*"]