Also adds xmlrpc-beta from PECL (PHP8 moved the extension there)
and setups max_input_vars=5000 as initial value (see MDL-71390).

Note that this also includes a tiny modification when configuring
redis sessions, because there was some outdated code from old issue,
now fixed (MDL-60978), so that info has been removed.

Adam Olley authored Apr 16, 2021 and Jake Dallimore committed May 07, 2021

Without this, people can craft URLs that other users might use not realising
what they do - and as a XSS vulnerability, it could do any number of things the
clicking-user has access to do on the site.

Change-Id: I82adc71e8706d8929011b4b24523d5b62b8ccea1

Marina Glancy authored Feb 17, 2021 and Eloy Lafuente committed May 06, 2021

passing null to getdate() has different results in PHP7 and PHP8

See also 643b0cca.

because of changes in PHP8 the '' == 0 is no longer true and the error in the google api wrapper was discovered

 * The button to "Add group/grouping access restriction" under
   common module settings should only be present if corresponding
   availability plugins are enabled; and
 * Prevent the same button behaving as a submit button, which
   intercepted the user hitting return in the form and added a
   restriction without deliberate action taken by the user.

This isn't really a deprecations where something is replaced
by another and all uses must adapt to. Instead it's just a
fallback functionality that will stop working in Moodle 4.2.

Because of that, I've tried to add TODO/@todo comments to
the places that will need to modified, always pointing to
MDL-71421 that is where the removal will happen.

Also, haven't added any debugging() output, after thinking
a lot about it, because this isn't anything that developers
can be using but a internal implementation detail (a fallback)
that we want to remove in some versions.