fix: wrong subquery error returning as 400 status

src/PostgREST/Error.hs

@@ -457,6 +457,10 @@ pgErrorStatus authed (SQL.SessionUsageError (SQL.QueryError _ _ (SQL.ResultError
         "23503"   -> HTTP.status409 -- foreign_key_violation
         "23505"   -> HTTP.status409 -- unique_violation
         "25006"   -> HTTP.status405 -- read_only_sql_transaction
+        "21000"   -> -- cardinality_violation
+          if BS.isSuffixOf "requires a WHERE clause" m
+            then HTTP.status400 -- special case for pg-safeupdate, which we consider as client error
+            else HTTP.status500 -- generic function or view server error, e.g. "more than one row returned by a subquery used as an expression"
         '2':'5':_ -> HTTP.status500 -- invalid tx state
         '2':'8':_ -> HTTP.status403 -- invalid auth specification
         '2':'D':_ -> HTTP.status500 -- invalid tx termination