feat(discretization): Added SystemLayout and associated helpers to allow for more robust access to parts of the block system

src/include/serif/discretization/blocks/base.hpp

@@ -14,6 +14,17 @@ namespace serif::discretization::blocks {
      */
     struct block {};
 
+    /**
+     * @enum RepresentedValueKind
+     * @brief Enum representing the kind of value a block represents, either a physical quantity (value) or a residual (residual).
+     *
+     * Generally this is mostly used in the solver/normalization system.
+     */
+    enum class RepresentedValueKind {
+        value,             ///< A value representing a physical quantity (e.g., temperature, pressure).
+        residual           ///< A residual representing the difference between the current state and the desired state in a numerical method.
+    };
+
     /**
      * @struct residual_block_base
      * @brief Base class for residual blocks, derived from block.