* New button allows to create standard issuer for nextcloud
* Since the endpoints url has to be https and nextcloud relys on the
baseurl to create the endpoints, the baseurl of issuers has now to be
https as well (or empty).
* Google's baseurl was changed to https (there was no reason not to),
whereas Facebook and Microsoft baseurls remain empty.
* In case of the creation of a nextcloud issuer, the baseurl is
required.
* Nextcloud requires the baseurl, therefore a parameter is added to
create_standard_issuer($type, $baseurl = false). That parameter not
required (or used) for anything but Nextcloud.
* Splitted the initialization of default values for issuers, the
creation of the issuer, and the creation of its endpoints. This is
a fix for following use case:
1. A user creates a standard issuer.
2. She cancels the form.
3. However, the issuer was already created. Thus, the cancel had no
effect.
* The function create_standard_issuer($type) can still be used to create
issuers programmatically if all required data is known beforehand (e.g.,
during upgrade or in tests).
Show the username and email of the connected system account (if it ever requires refreshing - this will help identity the account
to re-authorise).
Part of MDL-58220
