This is to avoid accidental misconfiguration while copy/pasting the
password value.

There is no point pre-compiling the theme SCSS if it is not stored somewhere that is available
to all webserving nodes. Localcache needs to be backed by the MUC cache.

Conflicts:
	mod/assign/styles.css

The new recordset support for Postgres requires transactions and
will cause errors if recordsets are not closed correctly. This
commit fixes problems that were identified during unit tests, and
via some basic code analysis, across all core code. Most of these
are incorrect usage of recordset (forgetting to close them).

On Postgres, get_recordset_sql loads all the results into memory
(within the Postgres library, which doesn't count towards the PHP
memory limit, but does count towards making your server run out of
memory) as soon as the query completes.

This commit changes the code to use cursors, which in Postgres
allow the results to be returned in smaller chunks (by default
100,000 rows).

Before MDL-59854 it was possible to have duplicate forum subscriptions.
Trying to import backups created from back then, caused a DB exception
due to unqiue key constraints. Now only one of multiple identical forum
subscritions is restored.