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

tests/discritization/domain/relation/relations.cpp

@@ -0,0 +1,36 @@
+#include <catch2/catch_test_macros.hpp>
+
+#include "serif/discretization/domain/physical_domains.hpp"
+#include "serif/discretization/domain/relation/relations.hpp"
+#include "serif/discretization/domain/types.hpp"
+
+#include "serif/tests/test_tags.hpp"
+#include "serif/tests/discritization/domain/domain_test_utils.hpp"
+
+namespace domain = serif::discretization::domain;
+
+TEST_CASE(
+    "Domain Boundary Relations Accept Exactly One Or Two Domains",
+    tags::unit &tags::mesh &tags::utils &tags::domain
+) {
+    STATIC_REQUIRE(
+        domain_test_utils::CanFormDomainBoundary<
+            domain::InfinitySurfaceBoundary, domain::VacuumDomain>
+    );
+
+    STATIC_REQUIRE(
+        domain_test_utils::CanFormDomainBoundary<
+            domain::StellarSurfaceBoundary, domain::StellarDomains,
+            domain::VacuumDomain>
+    );
+
+    STATIC_REQUIRE_FALSE(domain_test_utils::CanFormDomainBoundary<domain::StellarSurfaceBoundary>);
+
+    STATIC_REQUIRE_FALSE(
+        domain_test_utils::CanFormDomainBoundary<
+            domain::StellarSurfaceBoundary, domain::CoreDomain,
+            domain::EnvelopeDomain, domain::VacuumDomain>
+    );
+
+    CHECK(true);
+}