Add DIContainer singleton with key path registration

Sources/LuminateCore/DIContainer.swift

@@ -0,0 +1,34 @@
+import Foundation
+
+@MainActor
+public final class DIContainer {
+
+    public static let shared = DIContainer()
+    public private(set) var values = InjectionValues()
+
+    private init() {}
+
+    public func register<T>(
+        _ keyPath: WritableKeyPath<InjectionValues, T?>,
+        value: T
+    ) {
+        values[keyPath: keyPath] = value
+    }
+
+    public func resolve<T>(
+        _ keyPath: KeyPath<InjectionValues, T?>
+    ) -> T {
+        guard let value = values[keyPath: keyPath] else {
+            fatalError(
+                "DIContainer: No value registered for \(keyPath). "
+                + "Call DIContainer.shared.register(\\.key, value:) during app startup."
+            )
+        }
+        return value
+    }
+
+    public func reset() {
+        values = InjectionValues()
+    }
+
+}