Provide support data: URLs for mdui:Logo
Provide support data: URLs for mdui:Logo

There are currently over 600 logos in the eduGAIN feed that are specified
using RFC 2397 data: URLs. However, PHP's FILTER_VALIDATE_URL filter has
no explicit support for data: URLs, and consequently makes the assumption
they must follow a <scheme>:<host> format. The result is that arbitary
limitations are placed on data: URLs, causing all but a very small number
to fail this validation.

cf https://github.com/php/php-src/blob/php-7.3.0/ext/filter/logical_filters.c#L587

simplesamlphp/saml2