Various fixes

Fix OAuth and Realtime issues introduced in 9a515b9234

[DATABASE] Fix an empty default value mistake introduced in
fde929b151

[DATABASE][PostgreSQL] Avoid use of pg_constraint.consrc, which was removed in
PostgreSQL 12.

[DATABASE][MariaDB] Fix a typo introduced in aed2344bd4

[DAEMON] Wrap an assignment inside "switch":
a follow-up to adc689cb15

lib/database/pgsqlschema.php

@@ -328,7 +328,8 @@ class PgsqlSchema extends Schema
     {
         $data = $this->fetchQueryData(
             <<<END
-            SELECT "cols"."attname" AS "col", "con"."consrc" AS "check"
+            SELECT "cols"."attname" AS "col",
+                pg_get_expr("con"."conbin", "con"."conrelid") AS "check"
               FROM pg_constraint AS "con"
               INNER JOIN pg_attribute AS "cols"
               ON "con"."conrelid" = "cols"."attrelid"