feat: added new commands

- added follow command
- added unfollow command
- following command
- introduced logged in user middleware

internal/command/middleware.go

@@ -0,0 +1,20 @@
+package command
+
+import (
+	"context"
+
+	"github.com/StevanFreeborn/gator/internal/database"
+	"github.com/StevanFreeborn/gator/internal/state"
+)
+
+func requiresLoggedInUser(handler func(*state.State, database.User) error) CommandHandler {
+	return func(s *state.State) error {
+		loggedInUser, err := s.GetCurrentUser(context.Background())
+
+		if err != nil {
+			return err
+		}
+
+		return handler(s, loggedInUser)
+	}
+}