Fix unique foreign key in view (#1395)

test/Feature/QuerySpec.hs

@@ -1112,3 +1112,12 @@ spec actualPgVersion = do
 
   it "cannot use ltree(in public schema) extension operators if no extra search path added" $
     get "/ltree_sample?path=cd.Top.Science.Astronomy" `shouldRespondWith` 400
+
+  context "VIEW that has a source FK based on a UNIQUE key" $
+    it "can be embedded" $
+      get "/referrals?select=site,link:pages(url)" `shouldRespondWith`
+        [json| [
+         {"site":"github.com",     "link":{"url":"http://postgrest.org/en/v6.0/api.html"}},
+         {"site":"hub.docker.com", "link":{"url":"http://postgrest.org/en/v6.0/admin.html"}}
+        ]|]
+        { matchHeaders = [matchContentTypeJson] }

test/Feature/StructureSpec.hs

@@ -231,6 +231,23 @@ spec = do
               ]
             |]
 
+    describe "VIEW that has a source FK based on a UNIQUE key" $
+
+      it "includes fk description" $ do
+        r <- simpleBody <$> get "/"
+
+        let referralLink = r ^? key "definitions" . key "referrals" . key "properties" . key "link"
+
+        liftIO $
+          referralLink `shouldBe` Just
+            [aesonQQ|
+              {
+                "format": "integer",
+                "type": "integer",
+                "description": "Note:\nThis is a Foreign Key to `pages.link`.<fk table='pages' column='link'/>"
+              }
+            |]
+
     describe "PostgreSQL to Swagger Type Mapping" $ do
 
       it "character varying to string" $ do