Fix unique foreign key in view (#1395)

src/PostgREST/DbStructure.hs

@@ -393,7 +393,7 @@ allColumns tabs =
         array_to_string(enum_info.vals, ',') AS enum
     FROM (
         /*
-        -- CTE based on pg_catalog to get only Primary and Foreign key columns outside api schema
+        -- CTE based on pg_catalog to get PRIMARY/FOREIGN key and UNIQUE columns outside api schema
         */
         WITH key_columns AS (
              SELECT
@@ -409,7 +409,7 @@ allColumns tabs =
                pg_catalog.pg_class c,
                pg_catalog.pg_namespace n
              WHERE
-               r.contype IN ('f', 'p')
+               r.contype IN ('f', 'p', 'u')
                AND c.relkind IN ('r', 'v', 'f', 'm')
                AND r.conrelid = c.oid
                AND c.relnamespace = n.oid