In S2, E5, when Din Djarin (the Mandalorian of the title) fights against a Jedi, his Beskar armor is able to fully protect him from slashes from a lightsaber.
Is this a new concept introduced by Disney's The Mandalorian or has it been this way from the original Lucas's Star Wars universe?
I was under the impression a lightsaber could cut through anything but another lightsaber.