Adds spec for @@ operator and implements it in PgQuery

src/PostgREST/PgQuery.hs

@@ -175,6 +175,7 @@ wherePred (col, predicate) =
             "like" -> unknownLiteral $ T.map star value
             "ilike" -> unknownLiteral $ T.map star value
             "in" -> "(" <> T.intercalate ", " (map unknownLiteral $ T.split (==',') value) <> ") "
+            "@@" -> "to_tsquery(" <> unknownLiteral value <> ") "
             _    -> unknownLiteral value
 
     op = case opCode of
@@ -189,6 +190,7 @@ wherePred (col, predicate) =
          "in"  -> "in"
          "is"    -> "is"
          "isnot" -> "is not"
+         "@@" -> "@@"
          _     -> "="
 
 orderParse :: Net.Query -> [OrderTerm]

test/Feature/QuerySpec.hs

@@ -56,6 +56,10 @@ spec =
       get "/simple_pk?k=ilike.*YY*&order=extra.asc" `shouldRespondWith`
         "[{\"k\":\"xyyx\",\"extra\":\"u\"},{\"k\":\"xYYx\",\"extra\":\"v\"}]"
 
+    it "matches with tsearch @@" $
+      get "/tsearch?text_search_vector=@@.foo" `shouldRespondWith`
+        "[{\"text_search_vector\":\"'bar':2 'foo':1\"}]"
+
   describe "ordering response" $ do
     it "by a column asc" $
       get "/items?id=lte.2&order=id.asc"