feat: Refactors / moves into individual files, wip.

Sources/ComposableSubscriber/Internal/SetAction.swift

@@ -0,0 +1,32 @@
+import ComposableArchitecture
+import Foundation
+
+@usableFromInline
+enum SetAction<State, Action, Value> {
+  case operation(f: (inout State, Value) -> Effect<Action>)
+  case keyPath(WritableKeyPath<State, Value>, effect: Effect<Action>)
+  case optionalKeyPath(WritableKeyPath<State, Value?>, effect: Effect<Action>)
+
+  @usableFromInline
+  func callAsFunction(state: inout State, value: Value) -> Effect<Action> {
+    switch self {
+    case let .operation(f: f):
+      return f(&state, value)
+    case let .keyPath(keyPath, effect):
+      state[keyPath: keyPath] = value
+      return effect
+    case let .optionalKeyPath(keyPath, effect):
+      state[keyPath: keyPath] = value
+      return effect
+    }
+  }
+  
+  @usableFromInline
+  static func operation(_ f: @escaping (inout State, Value) -> Void) -> Self {
+    .operation(f: { state, value in
+      f(&state, value)
+      return .none
+    })
+  }
+ 
+}