feat(mean_field): added dimensions, discritization, and start of eos

The full rewrite of mean_field into something maintainable is progressing. dimensions is mostly done, discritization (domain, blocks, and fields) is done, and eos is progressing quickly

src/include/serif/discretization/domain/relation/concepts.hpp

@@ -0,0 +1,11 @@
+#pragma once
+
+#include "serif/discretization/domain/relation/relations.hpp"
+#include "serif/utils/misc/std_helper/cleaning.hpp"
+
+namespace serif::discretization::domain::relation {
+    using utils::misc::std_helper::AIsBaseClassOfB;
+
+    template <typename R>
+    concept IsRelation = AIsBaseClassOfB<R, DomainRelation>;
+}